Prices are for the least and most expensive main dishes at lunch (L) and dinner (D). Credit cards are indicated by letters: AE (American Express). DC (Diners Club), CB (Carte Blanche), MC (Mastercard) V (Visa) and C (Choice). "free parking" indicates establishment has a lot; otherwise, expect street parking or commercial lots. "smoking prohibited" means that smoking is not permitted in the entire restaurant; "no-smoking section" indicates a separate seating area for non-smokers. "Full bar" indicates the establishment is licensed to sell spirits and beer or wine. Information preceding the reviews was supplied by the restaurants themselves. AMERICAN CAFE 227 Massachusetts Ave. NE. 547-8500. 1211 Wisconsin Ave. NW. 337- 3606. 5252 Wisconsin Ave. NW. 363-7773. L, D $3.95- $9.95. L, D daily. Sun brunch. AE, MC, V. Reservations accepted only at Capitol Hill for parties of five or more. Free parking for two hours at upper Wisconsin Ave. branch. Full bar.

The choice is easy at the American Caf,e: ask for things without: raw vegetables without house dressing, cold, smoked leg of lamb, smoked turkey or chicken, California salad, garden salad or fruit salad, all with dressings on the side. Soups are good choices if a clear one--say, vegetable--is available. The kitchen has fresh fruit and plain meats, but tuna, broccoli or cucumber salad are made in advance with dressing at a central commissary. Accompany your meal with mineral water (two kinds) or tea (also two kinds). BERWYN CAFE 5010 Berwyn Rd., College Park. 345-2121. L, D $3.75. L, D daily. Closed Sun. No credit cards. No reservations. Free parking. Smoking prohibited. No alcoholic beverages.

A half-dozen years ago, the Berwyn Caf,e served delicious and carefully prepared food. Now they've too often gone the way of convenience, serving frozen tofu burgers, packaged tofu dressing spread on predictable salads and pita- bread sandwiches. The Saturday special--whole- wheat pizza--tastes like leftovers. Some soups are good, and sandwiches are fine. But the doughy and sour spinach triangle and the grainy leaden pastries suggest you'd eat better if you grazed at the excellent produce and refrigerator sections of the grocery in front. THE COMMUNITY CAFE 4949 Bethesda Ave., Bethesda. 986-0848. L, D $2.25-$6.90. L daily, D daily ex Sat. Closed Sun. No credit cards. No reservations. Free parking. Smoking prohibited. No alcoholic beverages.

At the Bethesda Avenue Co- op's Community Caf,e, the food is vegetarian, mostly sandwiches and salads with a daily special ranging from eggplant curry to tofu ranchero; and Monday night is Mexican night. There are homemade (but disappointingly wan) soups and a bright, frisky-looking salad bar. The sandwiches are big and sloppy, oozing avocados and sprouts, and can be washed down with lemonade made with spring water, herb teas or nutritionally approved sodas. CHARLIE CHIANG'S 1912 I St. NW. 293-6000. L $4.95-$6.95, D $5.50- $16.95. Open daily. AE, CB, DC, MC, V. Reservations suggested. Free valet parking after 5:30 p.m. Full bar.

The restaurant's response to our questionnaire--that it had "vegetables and Chinese salads" as diet foods--sent me there for lunch. But when I arrived, the waiter insisted the kitchen was too busy to deal with any special requests. Only saut,eed food was available; steaming anything would take too long, he said. Even though we told him we'd been promised diet food, he refused even to ask the kitchen or the management if our requests were possible. We settled for wonton soup--thin and on the bland side, but greaseless if we left the ham alone--and the two non-diet dishes. Then the hostess wandered by and recognized me as a restaurant critic. I explained our dilemma, and she acted appalled with the waiter. She got us a Chinese chicken salad without oil and offered us steamed scallops with vegetables. And she sent a new waiter as well. The chicken salad, with bean sprouts and julienned cucumber, was indeed delicious, but largely because of the sesame oil that coated it. And the scallop dish, perfectly cooked and with crunchy green broccoli and chunks of red bell pepper, was exceptional. But it, too, was glistening with oil. We ate, we guiltily enjoyed, we paid (about $20 after club sodas, tea and tip). And we vowed to diet elsewhere. DOMINIQUE'S 1900 Pennsylvania Ave. NW. 452-1126. L $6.95- $14.95, D $8.95-$23.95. L daily ex Sat, D daily. Closed Sun. AE, C, CB, DC, MC, V. Reservations suggested. Free valet parking at dinner. Full bar.

Dominique's reputation for being accommodating stands firm, whatever your diet. We could have chosen a variety of things straight from the menu for a low-calorie dinner: grilled or baked fish, cold lobster, veal or lamb. Appetizers include all the usual seafood cocktails, cold or hot asparagus with lemon or thin slices of smoked buffalo draped over melon. For a main course, we asked for venison ($15), which is lean enough to serve a diet; it came gamy and tasting a little singed, but rare and tasty and accompanied by steamed vegetables--all fresh and firm. Dover sole ($18) was an even better diet dinner, steamed under a layer of julienned carrots and zucchini, sliced mushrooms and snow peas criss-crossing the top. It came with even more steamed vegetables. The waiter was thoughtful enough to ask, once we had specified that we wanted no fats, whether salt was all right. And for dessert the kitchen arranged strawberries, melon, and kiwis as prettily as any tart. You can expect a three-course meal to run $30 to $35 a person with tax and tip, and a staff warmly supportive of your caloric restraints. FOOD FOR THOUGHT 1738 Connecticut Ave. NW. 797-1095. L $3.25- $4.25, D $4.95-$5.95. L daily ex Sat, Sun, D daily. No credit cards. No reservations. No smoking section. Full bar.

Food for Thought treats vegetarians to zesty fresh cooking while it punishes meat eaters with turkey roll. So stick to the plant world and enjoy the food and the low prices. The menu is filled with whole grains, hot dogs free of nitrites, meatless main dishes, fresh fruits, caffeine-free beverages, herb teas or just a plain hard- boiled egg. You could splurge on an imported beer or a bargain-priced wine, or restrict yourself to saut,eed vegetables and brown rice. You can even order just raw sunflower seeds. There is yogurt dressing for salads, though neither the dressing nor the salad is anything to strengthen your resolve. GERMAINE'S 2400 Wisconsin Ave. NW. 965-1185. L $5.95-$9.50, D $8.25-$24.95. L daily ex Sat, Sun, D daily. AE, CB, DC, MC, V. Reservations suggested. Full bar.

Look for a slim chef if you want to diet in a restaurant without a struggle--or at least a chef with slim spouse. Dick Swanson has been dieting this year, so his wife, Germaine, is ready to deal with calories. Start a dinner for two with a single order ($5.50) of raw scallops marinated in lemon, ginger, hot pepper and dill, on a bed of shredded lettuce and a starburst of snow pea triangles --beautiful, tantalizing, refreshing. The two main dishes were too large for dieters but too good for restraint. A salmon fillet had been wrapped in foil with lemon juice, dill, ginger and a touch of soy sauce, on a bed of onions with a garnish of snow peas and a carrot flower ($15.25). It was grilled to exactly the right juicy moment and slit open at the table. Chicken breast-- skinned and boned--came as teriyaki ($10.50), charcoal grilled and still juicy, brushed just with soy rather than the usual sugary teriyaki sauce, and served on a ring of bright green and crisply boiled broccoli florets. Plain rice and jasmine tea filled out the meal, and there is always ripe, sweet Hawaiian pineapple, and often another fresh fruit or two for dessert. HEALTH'S A-POPPIN 2020 K St. NW. 466-6616. Br, L $2.30-$4.95. Br daily ex Sat, L daily. Closed Sun. No credit cards. No reservations. Beer and wine only.

The cafeteria line has salad makings for nearly any diet: chickpeas, raw vegetables, cold cooked vegetables and various cheeses. You can get tuna with no dressing, although the chicken and shrimp salads are already mayonnaised. There is no low-fat dressing among the several choices, but there are little plastic cups of vinegar for salad. Every day, Scarsdale dieters are honored with an appropriate diet plate. There are yogurts galore and whole- grain breads, fresh fruits and herb teas. One might hope for more knowledgeable servers in the cafeteria line, but for $5 to $10, lunch is an easy task for a dieter here. IRON GATE INN 1734 N St. NW. 737-1370. L $3.75-$9.25, D $6.50- $9.50. Open daily. AE, MC, V. No reservations at lunch, suggested at dinner. Full bar.

The idea came from the restaurant's answer to our query: grilled chicken with sumac and fresh unbuttered vegetables were available for diets, we were told. Nobody clued in the waiter, however. He could suggest nothing more than a salad of greens, feta and ham (!) with no dressing. When we pressed him about grilled chicken (not available), then kebabs, he did agree we could get kebabs with no oil or butter. Did we want rice? Not unless it was cooked without oil or butter. That set off a tirade about how you couldn't cook rice without oil. Finally, we agreed on a meal, and he turned benign and served with great attention. What we got was one order of cornish hen (there is no chicken, he reiterated), grilled dry and with a nice smoky crustiness, though overcooked and rather stringy. The portion, three breast quarters, was huge. The other plate was shrimp--large, tasty, grill-singed and juicy but apparently brushed with oil. Both were preceded by a standard green salad with chopped tomato and shreds of red cabbage--and no dressing. And both were accompanied by grilled peppers, onions and tomatoes, plus a side dish of sliced tomatoes sprinkled with parsley. It was a satisfactory lunch for $20 including tip ($6.50 for the chicken, $9.25 for the shrimp). But one wouldn't, if this was typical, seek out the Iron Gate for diet food. KALORAMA CAFE 2228 18th St. NW. 667- 1022. L $2.95-$4.75, D $5.95-$8.50. Sun brunch, L daily, D daily ex Sun. Closed Mon. No credit cards. Reservations accepted, required for five or more. Beer and wine only.

Kalorama Caf,e is clearly health-oriented, from its fresh products cooked from scratch to its serving of only whole grains and fresh fish--no meat. And the prices are right: $7 for broiled fish with brown rice and a big, colorful and very fresh salad, the same price for a monumental plate of pasta. When we asked for something with no fat--no oil or butter or cream--the waitress volunteered to check with the kitchen, and came up with the broiled fish, moistened with broth. We asked whether the spinach noodles with herbs and garlic could be made with yogurt instead of cream, and the cook agreed to try. We were miffed partway through the pasta, to realize it was heavily laced with cheese; surely the kitchen should have realized that if we didn't want cream we wouldn't want cheese --or at least it should have been mentioned. It was a tasty dish nonetheless and better than the fish, which was perfectly cooked--moist and tender--but bitter. The brown rice was dry, but what could we expect with the restrictions we imposed? We were less patient with the limp condition of the vegetables we ordered as an appetizer to dip in herbed yogurt. Kalorama Caf,e has willingness and menu possibilities, but dieters need to be very specific about what they want and don't want. LE GAULOIS 2133 Pennsylvania Ave. NW. 466-3232. L, D $2.75- $14. L daily ex Sat, D daily. Closed Sun. AE, C, MC, V. Reservations suggested. Full bar.

Le Gaulois makes dieting easy. There are three "cuisine minceur" entrees on the menu, although the steamed vegetable plate (at under $5), may come with butter on some of the vegetables. In any case, ours was on the soggy side and far less interesting than the other two cuisine minceur possibilities. The delectable veal scallops, lightly saut,eed (ask for no butter and you'll get a minimum) are arranged on a bed of celery root pur,ee, then smothered in a julienne of carrots and zucchini. Rockfish baked in foil with tomatoes, zucchini and dill is also good, lacking nothing in its eschewal of butter and cream. Or start a meal with belon oysters to dip in a vinegar-shallot sauce mignonette or maybe a plpeatter of smoked trout, eel, shrimp and superb smoked salmon. Then end with fresh fruit (ask that the fruit salad listed as an appetizer be served free from sugar syrup). It will cost about $50 a couple once you have had a Perrier and coffee or tea, and left a tip. And be warned that the kitchen can be light on butter but heavy on the salt. LUNCH BOX Carryout locations: 1700 Pennsylvania Ave. NW. 393-2571. 1721 G St. NW. 393-3667. 1622 I St. NW. 833-9538. 825 20th St. NW. 296-0620. 1090 Vermont Ave. NW. 289- 2098. Seating available at: 1719 M St. NW. 775-1652. Br, L $1.30-$3.25. Br, L daily. Closed Sat, Sun. ex 1719 M St. open Sat. No credit cards. No reservations. No alcoholic beverages.

Forget fast food if you are on a diet. But at least as fast and much less caloric are the turkey sandwiches at the Lunch Box outlets. The bird is freshly roasted and sliced sufficiently thick. For $2.20 you can have it on white or pumpernickel, but add 15 cents to get it on whole-wheat pita. Hold the mayonnaise and expect it to taste dry, but ask for plenty of tomato and lettuce to overcome that. Round out your lunch with orange juice (55 cents for 10 ounces), herb tea or brewed decaffeinated coffee, and finish with a bowl of strawberries (95 cents) or a choice of whole fruits--bananas, apples, oranges, pears--but don't expect them to be ripe when you want them. MEL KRUPIN'S 1120 Connecticut Ave. NW. 331-7000. L $5.95- $9.95, D $10.95-$17.95. L, D daily. Closed Sun. AE, CB, DC, MC, V. No reservations at lunch, suggested at dinner. Free valet parking at dinner. Full bar.

They may look big, but they're all on diets in Mel's. Newsmen eat merely a plate of oysters; editors have only a chef's salad--hold the dressing. The waiters are willing to bring chicken salad ($7) without mayo--just with chopped celery, green pepper, egg and parsley. It is a nice, crunchy fresh m,elange, but be sure to ask for lemon to zip it up. Or start with oysters or shrimp, continue with broiled fish, a dressing-free salad or chicken- in-the-pot without the matzo ball. As for salt-free diets, if you skip the pickles and the soups you'll find that Mel's food is aimed for bland tastes, so you won't be in danger of overzealous spicing. You can't depend on the waiters to understand your diet ("there's no oil on it, just a little mayonnaise") but you can count on them to recognize dieting as normal human activity. MONTPELIER ROOM (In the Madison Hotel), 15th & M Sts. NW. 862- 1600. L $8-$18, D $16.50- $24. Br daily ex Sat, Sun brunch, L daily ex Sat, D daily. AE, CB, DC, MC, V. Reservations suggested. Full bar.

On our questionnaire the Montpelier Room answered that the staff could provide a diet meal with eight hours' notice, which we gave them. It was unnecessary and irrelevant. They were gracious about our dietary needs, warning us that the lentil soup had hot dogs in it. Thus, with waiters offering tableside flourishes and frequent attention, we ate high-quality consomm,e ($4) and smoked trout that was too salty and dry but grandly served with horseradish (and sour cream to ignore) in clam shells, dilled cucumbers and red onion on the side ($9). For main dishes, chicken ($16.50) and Dover sole ($22.75) were grilled, both nicely and not too long for moistness, though the sole was oversalted. But best were the vegetables: green beans and carved boiled potatoes. Carrots came buttered, but the waiter cheerfully took them back for plain ones. For dessert, there are fresh berries, melons and --a rare treat--fresh fruit salad that has not been presweetened. The food may be unexciting, but it is high quality and for your $40- a-person meal you get your money's worth in service. NORA 2132 Florida Ave. NW. 462-5143. L $7.50-$13, D $10-$16. L daily ex Sat, D daily. Closed Sun. No credit cards. Reservations suggested. Full bar

Nora's menu boasts additive-free meats and emphasizes what's seasonal and fresh. There is always fresh fish, chicken, fresh vegetables, fruits and even brown rice. Ceviche is one of the restaurant's best dishes, and it contains no oil but only baby scallops with lime juice, hot green peppers with a touch of red for color. The gravlax is also fine if salt is not a problem. As a main course, the chef was willing to leave the cream cheese sauce off fettucine primavera, so we had the homemade noodles tossed with steamed, crunchy and colorful snow peas, red bell peppers, broccoli and scallions. He also left off the salt, so we added salt and pepper at the table. The Indonesian sat,e was well-trimmed pork marinated in lemon, cumin and coriander and grilled on skewers. It came with crunchy brown rice and julienned carrots and zucchini that were already buttered. For dessert, there are berries in season, or you can splurge on homemade sherbets. Dinner may cost $25 a person, but it will cure the diet doldrums. PETITTO'S 2653 Connecticut Ave. NW. 667-5350. L $4-$10, D $6.50-$14. L daily Sat, D daily. Closed Sun. AE, CB, DC, MC, V. Reservations suggested. Full bar.

Since the restaurant had noted on our questionnaire that it had diet offerings, I called ahead. The woman on the phone, though, concluded that there was nothing appropriate on the menu. "I could always get a salad," I suggested, to which she responded, "There's a charge of $4 if you don't get a main course." Further probing brought her concession, "I guess you could get something." At the restaurant, the waiter, though familiar with the ingredients of every dish, was lazy. No, everything was saut,eed, and the pasta would stick together without oil. The hostess suggested: we could get fettucine with tomato sauce that had just a touch of butter. We decided to start with a tossed salad, hold the cheese and dressing. It came with dressing. Clearly becoming impatient with us, the waiter took it back for an undressed salad, which was crisp and good. Forty-five minutes after our arrival we got water; 50 minutes after, we got our main dishes. The sea trout, though doused with paprika, was a moist and carefully grilled fillet with a touch of wine. The fettucine was tempting--al dente noodles with a light and delicate herbed tomato sauce-- but was laced with cheese. Nobody had mentioned cheese, and it certainly was not on our diet, but we dared not tackle our impatient waiter again. We ate as little of the fettucine as we could manage, given that it tasted so good, and finished with Crenshaw melon. All that cost us $34 for two (trout $11.50, pasta $7). The verdict: good food, but too much of a trial. PICCOLO MONDO 1835 K St. NW. 223-6661. L $7.95-$9.95, D $12.25- $15.50. L daily ex Sat, D daily. Closed Sun. AE, DC, MC, V. Reservations suggested. Full bar.

There is a gulf between not doing anything wrong and doing things well, and Piccolo Mondo fell into that gulf. The waiter was neutral toward our diet requests, a big step up from hostile waiters we had encountered elsewhere. We could get broiled salmon, swordfish or a veal chop, he suggested. A little fresh tomato sauce or something slightly more inventive, we suggested? No, he stuck to his guns. We started with soups--chicken broth with spinach and egg, tortellini in chicken broth, each $3.50, large and steaming--and found them fat-free, but pale and nearly tasteless. The veal chop ($15.50) was a fine hunk of meat, well trimmed and grilled to a crusty surface and faintly rosy interior. Salmon was cut thick but broiled to a dry and tasteless state, unseasoned and slightly fishy, accompanied by a raw tomato half and boiled potatoes--dull fare but at least some contrast. We've had far better grilled fish for less than $16. For dessert we could have had kiwis or strawberries but chose raspberries, which turned out to be $6.50 a portion and partly moldy. There was excellent coffee, and a bill of $55 before tip for a boring dinner. RADISHES AND RAINBOWS 1101 Connecticut Ave. NW. 223-8880. Br, L, $1.85-$3.95. Br, L daily. Closed Sun. No credit cards. No reservations. No alcoholic beverages.

I had hopes. It is such a fresh and imaginative carryout, with bright and colorful salads and vegetable- or otherwise- stuffed pita sandwiches. But the low-calorie dressing ("Italian") tastes of factory fabrication. While a small salad ($1.65) looks prettily carrot- and-mushroom-topped and surrounded by cucumber slices, it is a veneer over iceberg and romaine lettuce. The vegetable-laden sandwiches and salads are good diet food in themselves, but where are the homemade low-fat dressings we had been hoping for? RIVE GAUCHE 1312 Wisconsin Ave. NW. 333-6440. L $6.75-$12, D $12.50-$16. Open daily. Sun brunch. AE, CB, DC, MC, V. Reservations suggested. Free valet parking. Full bar.

I asked chef Michel Laudier to make a diet dinner for two. And he provided us with an excellent meal that is a French chef's conception of self-denial. First came consomm,e with mushrooms--shiitakes, morels and more everyday varieties-- under a balloon of puff pasty. If you're on a diet, he explained, you needn't eat the pastry. Next an hors d'oeuvre of grandeur: two succulent legs of quail, a morsel of smoked salmon, a medallion of lobster centered with caviar, a hillock of julienned endive and truffles and two kinds of greens, all dressed with walnut and olive oil. So much oil on a diet? It was virgin olive oil with apple cider vinegar, very pure and healthy, explained Laudier. The three veal medallions that followed had been saut,eed, then degreased and sauced with a reduction of madeira and neither flour nor fat. It was all the more appealing for its garnish of turnip batons (caramelized) and spinach (buttered). And what about the two pommes souffl,es? They were the only starch in the meal, he shrugged, and after all they were "mostly air." Dessert, too, was mostly air, a very light souffl,e made only of egg whites, raspberries and enough sugar to cut their tartness. We were expected to wave away the whipped cream the waiter proffered, though we fell for the raspberry sauce. Such a meal can be expected to cost in the $30-per-person range, and is indeed both light and elegant; but don't try to get away with it as diet food. SAKURA 7926 Georgia Ave., Silver Spring. 587-7070. L 5.50- $19, D $14-$20. AE. Reservations suggested. Free parking. No smoking section. Full bar.

Nowhere are dieters welcomed more visibly than at Sakura, where the menu lists an entire page for "those on a special diet" and a card encourages people with food allergies to alert the management. On the diet menu are bean curd dishes: chilled tofu with a dip of ginger, scallion and fish flakes; tofu boiled in kelp soup, fried or combined with vegetables. One grand dieters' dish is chirinabe, a bowl enough for two of broth in which have been simmered chunks of fish, cabbage, onions, spinach, mushrooms and bean curd, with a soy-vinegar sauce to dip or mix in. The bowlful, depending on the fish, costs $8 to $13; the tofu appetizers are under $3. And the rest of the menu, from the six-course vegetarian special dinner to sashimi, sushi and several boiled or broiled fish and meat dishes remind us that Japanese food is as fresh, simple and healthy as a cuisine can be, except for the salty seasonings, which are often added at the table anyway. SHEZAN 913 19th St. NW. 659- 5555. L, D $4.75-$14.50. L daily ex Sat, D daily. Closed Sun. AE, CB, DC, MC, V. Reservations suggested. Free parking. Full bar.

Fish or chicken: dieting in restacompaniurants easily locks into a routine. So Shezan offers a new set of flavors for your fish and chicken. You want your fish or chicken grilled without oil or butter? No problem. And the marinated red-gold charcoal- grilled chicken automatically comes sans skin. Start with a lovely, homemade chicken broth sprinkled with herbs and afloat with shred of vegetable for some crunch. The menu usually lists papaya among the appetizers, another appropriate start. Or a green salad with lemon. Your diet may warrant some bread; in this case you will be lucky enough to find whole-wheat naan, a floppy and delicious thin pancake shape, without butter. You can also have fish or shrimp marinated in turmeric-yellow and sweet-smelling spices, then grilled without grease; but the shrimp come with a well-oiled rice pilaf that tests your will power; ask for plain rice. And don't be fooled into thinking the raita, a cucumber and yogurt side dish, will do; it is sweetened and studded with raisins. For dessert you might have papaya if you missed it to start. In all, the prices are on the high side (with shrimp at $10.75 and chicken at $8, the lunch tab mounted rapidly to about $40) but the service is accommodating. Dieting is so taken in stride that the waiter even reminded us that crab salad was already dressed with oil, so we might want to order something else. SWEET JASSMINE 4626 14th St. NW. No phone. D $2-$4. D daily. Closed Sun, Mon. No credit cards. No reservations. No alcoholic beverages.

There are only five tables, and the menu consists of a soup, a salad and a mere three entrees; but Sweet Jassmine is doing a brisk eat-in and carryout business. The reason is simple: a really good cook in the kitchen makes this probably the best vegetarian restaurant in the area. There is always a tossed green salad with delicious sesame-lemon dressing. And there are salads such as minty tabulleh, red beans with the crunch of onions and peppers, creamy potato and zesty coleslaw. We tried a vegetable soup made intriguing with cracked wheat to thicken it, squash and onions to season it. And main courses were eggplant with a nongreasy crumb crust and topped with cheese and tomato, black-eyed peas and cabbage and a fiery, delicious combination of Chinese dishes --dan dan noodles made with whole wheat pasta, and Szechuan vegetables that were crisp and bright and under the hot-chili fire. To drink, choose apple cider hot or cold, or a very good Red Zinger punch; and desserts are homemade of whole grains. This food reminds you there need be nothing routine about vegetables. TAVERNA CRETEKOU 818 King St., Alexandria. 548-8688. L $3.50-$9.50, D $3.50-$14.50. L, D daily. Closed Mon. AE, DC, MC, V. Reservations suggested. Free parking. No smoking section. Full bar.

When we called Taverna for reservations and said we were dieting, the hostess cheerfully suggested all kinds of light meals. And in truth the menu does offer cucumbers in yogurt with mint as an appetizer, several salads or a tangy and warming egg-lemon soup if eggs fit your restrictions. For main courses the kitchen will leave the sauce on the side for swordfish kebab or grill a fine fresh whole rockfish with lemon until its skin is crisp and its interior moistly steamy. On the meaty side are very lean and ungreased lamb kebab, lamb roasted and sliced or chicken grilled with oregano and lemon. Good food, a lovely room and dashing and efficient waiters make a Taverna dinner a pleasure at no great price (about $12 for the fish or lamb, a full dinner with tax and tip about $20 a person). The only disappointing note was that despite our plea for accompaniments with no oil or butter-- and the waiter's pledge to note that on the order--the spinach (delicious) was buttered, the roast potato (irresistible) had a richness that suggested oil, and the rice (wonderful) was permeated with something more caloric than water or broth. TED LIU 1120 20th St. NW. 223- 5160. L $5.25-$6pani.25, D $5.75-$20. Open daily. AE, CB, DC, MC, V. Reservations suggested. Free parking at dinner. No smoking section. Full bar.

It took only a little persuasion to get the waiter to ask the kitchen whether it could steam some scallops and some vegetables, and the waiter volunteered, once the kitchen agreed, that we might like garlic on the scallops. He also warned us that the hot and sour soup was greasy but that the chicken and corn soup was all right on that score. Could we get our lunch without MSG? Yes, he said. The result: a pleasant and mild chicken- corn soup, lightly thickened with cornstarch and not greasy, a won ton soup that tasted like salted water with a canned mushroom, a spot of Chinese cabbage and limp noodles tinged with meat. Main dishes were lightly steamed scallops ($6.25) with indeed a touch of garlic--nothing to inspire a dieter--and vegetables ($5.25) such as snow peas, water chestnuts, carrots, black mushrooms and bok choy, still a bit crisp and lightly glazed with cornstarched broth and a touch of sesame oil. With a glass of tomato juice (warm), a bowl of rice and a pot of tea, lunch came to just under $10 a person after tipping. We would have left feeling fairly treated if the MSG explosion hadn't hit. TUNNICLIFF'S 222 Seventh St. SE. 546-3663. L. D. $4.50-$13.50. Open Daily. AE, CD, DC, MC, V, Reservations accepted. Full Bar.

Tunnicliff's has mesquite grilling, nachos and regionalisms such as brunswick stew. The passing fancies and the best of the fashions--fresh fish and vegetables, a nice selection of California wines by the glass--are there. Furthermore, they are at reasonable prices and served in a pleasant set of rooms. But beneath all the fashion is too little substance. Each day there is a Pritikin and a Scarsdale selection, but the Pritikin meal we had was nothing that Nathan would recognize. A chicken breast had been skinned (good start) and stuffed with tarragon and vegetables (carrots, onions, cabbage), then bedded on more vegetables that were greasy. The chicken itself was dry and bland, certainly not worth all the oily calories surrounding it. The Scarsdale selection was stir-fried pimiento steak. You'd do better choosing for yourself, perhaps cold smoked trout or the mesquite-grilled fish. 2091/2 2091/2 Pennsylvania Ave. SE. 544-6352. L $12.95- $16.95, D $22. L daily ex Sat, D daily. Closed Sun. AE, CB, DC, MC, V. Reservations suggested. Full bar.

When you want a diet meal at a restaurant with such a small menu, you'd better check ahead. When I called one noontime about dinner that evening, the receptionist turned the phone over to the kitchen, where the lunch chef volunteered to leave a note for the dinner chef to leave out the butter in one portion of salmon baked in parchment. The salmon was delicious, quite fresh and topped with julienned vegetables and basil, cooked until just a touch underdone so it was moist. I forgot to ask the waiter to leave off the zucchini pancakes, however, and they are too tempting to expect a dieter to leave untouched. Dessert offers no choice for dieters, so dinner ended with brewed decaffeinated coffee and a bill of about $30 a person after tax and tip. VINCENZO 1606 20th St. NW. 667- 0049. L, D $9.50-$18.75. L daily ex Sat, D daily. Closed Sun. AE, MC, V. Reservations suggested. Full bar.

We wanted a low-fat meal, we explained to our waiter, and wanted to start with pasta. The waiter insisted no pasta could be prepared without oil. Surely, with clams and mussels and fresh tomatoes and basil in the kitchen, something could be concocted, we suggested. "Noodles, just boiled noodles," he insisted. I persisted, demanding that he ask the chef. That persistence brought pasta with clams, aromatic from the steaming juices and parsley. This wonderful beginning was followed by baked sea bass, two small whole ones per person where one would have sufficed, in a similar sea-tangy, herbed and faintly winey clear broth. The flesh was pearly white and juicy, and the preparation highlighted rather than overwhelmed its delicate flavor. That same6pani waiter had discouraged us from ordering the baked bass because "it will take 40 minutes," but we weren't intending to rush through our $50 meal, and ordered it anyway. Needless to say, it took nowhere near 40 minutes. There was also grilled fish, readily available with no oil or butter, crisp and smoky from the charcoal fire. The swordfish was a bit overcooked and tasted sooty, but it was of wonderful flavor. The waiter brought buttery little potatoes in their skins, but we sent them back for plain ones. In their stead he brought spaghetti- thin fresh green beans with a fainty herbalness but no oil, and fresh cauliflower, both cold and accompanied by a wedge of lemon. The meal was washed down with the slightly spritzy imported bottled water that comes to every table. Dinner was elegant, ending as it did with a plate of very perfumed raspberries and probably Washington's most authentic espresso. The waiter had offered fruit salad for dessert. Did it have sugar in it, we wondered. Just a little, he answered, commenting, "That's a pretty strict diet." And that's a pretty judgmental waiter we concluded, but a very understanding kitchen..