Open for lunch Monday through Friday, 11:30 a.m. to 2:30 p.m.; for dinner Monday through Saturday, 6 to 10:30 p.m. AE, BA, MC.

Food: High-quality classical French, more consistent at lunch than dinner.

Style: Sedate, with very professional service

Price: Complete dinners with wine from $25 a couple

TWO THINGS I RECENTLY discovered are: 1) It takes only about ten minutes to drive to Arlington from downtown Washington at lunchtime, and 2) L'Alouette is a good reason for doing so.

Washington, of course, has plenty of French restaurants, most of them grand and serious, not to mention requiring a serious financial commitment. But L'Alouette is one of those rare mythical enterprises known as "a nicne little French restaurant." That does not mean it is a cafe; the menu and service are classical. The menu covers the full range of filets of sole, quenelles, salmon in champagne sauce, duck with orange sauce, veal scallops, filets of beefs and rack of lamb, with appetizers from vichyssoise to fresh caviar, and desserts from caramel cream to souffles. The captain reels off a list of daily specials, which also appear on a blackboard in the window at lunchtime. From fresh flowers on the tables to dishes garnished with carved olives or puff pastry crescents, itis apparent that this is no casual enterprise. But the decor and the prices reveal a refreshing modesty.

Hardly two dozen tables are lined up in three rows down the length of the dining room; a few more fit into a small side room screened off by macrame hangings. What was once the barn-siding setting for La Bergerie has been repainted with a floral mural on a pale gray background, here and there gilded with framed bird paintings. Simple, a touch tea-roomy, quite pleasant. Among its ambient assets are handsome heavy glass contemporary cnadle holders; among its defects - Muzak at dinner.

A gracious maitre d'hotel and obviously experienced - if sometimes harried - waiters operate the dining room smoothly, attending but not hovering. Since the restaurant is fairly new and hasn't yet developed a heavy following, it has yet to be fully tested. So far they handle questions and complaints good-naturedly, and time their service well.

But the food is, after all, the point, and, unless my experiences were atypitcal, lunch is more consistent than dinner. Given the emphasis on daily specials - asparagus with sauce mousseline, zucchini or peppers stuffed with minced veal, veal pojarsky or herbed scallops of veal, fish filets basquaise eration. The asparagus have been - at least at lunch - carefully peeled and cooked, served with a tangy, light mayonnaise turned into a cloud with whipped cream. Mussels were sweet and plump, exploding with garlic-parsley butter. Mushroom soup, creamy and subtly tangy, seemed too much to eat room soup, creamy and subtly tangy, seemed too much to eat but a pity to leave. At lunch the sauces are light and glossy, though brown veal sauces have alternated between timidity and abandon with the herb jar. Even so, the crisply sauteed breaded veal, the moist stuffed vegetables, and the gently cooked fish filets were more than satisfying - and more than generous. A bacon-and-potato omelet was cooked with rare precision. Main dishes are preceded by a fine green salad tossed with a mustardy vinaigrette, and accompanied by the likes of saffron rice, browned potatoes, and fresh carrots with peas. With one of the moderately priced wines - which start at $5 and offer a decent choice under $10 - you can have a delightful lunch for under $10 a person including tip. It's worth saving room, though, for some of the desserts. The pear tart is crusted with an excellent short pastry, layered with liqueurlaced custard, and studded with sliced almonds. Strawberries are slathered with a sweet, winey sabayon as light as eiderdown. As for chocolate mousse, don't bother, lest it undo your image of your good lunch.

Although dinner offers one of the best buys among French restaurants (onion soup or pate, salad, coq au vin or filet of sole, tart or mousse, coffee and a bottle of wine for two for $25) the saucier is obviously not a night person. Whatever we tried - from delicate quenelles to perfectly rare filets - was cooked by someone who knows a great deal about timing and temperature. But the sauces, across the board, were flawed by overthickening, oversalting, or simply by having broken down into oil pools. We ate the lovely fish, enjoyed the pale veal. But we pushed the sauces aside. Even the mussels, so memorable at lunch, were soggy with bread crumbs and salty nearly beyond endurance; and the mousseline, so perky at lunch, had thinned and lost its excitement at dinner. All the flaws were in the sauces. The pate was a stunning presentation which lived up to its promise. The fish soup, thick and robustly accented with fennel, was grand. And the salad Alouette, a clever combinationo f spinach, watercress, mushrooms, endirve, tomatoes and walnuta, was worthy of spring.

Although a la carte entrees climb to $11.50 (a glorious platter of filet of beef, filet of veal and lamb chop with sauteed mushrooms, garlicky grilled tomato and sauteed potatoes), most are $6 to $8. Soups are $1.25 to $2.50, hors d'oeuvre mostly $2 to $3, and desserts average $1.50 to $2. With fixed price dinners including wine at $25 and $34 a couple, this restaurant is priced moderately for the quality of its cuisine and service. Lunch main dishes range from $3.75 to $6.75, and are a large meal in themselves.

You don't have to be a Virginian for L'Alouette to be worth the trip.