The American salad bar is a wondrous thing. It can include vegetables raw and cooked, of every hue known to nature. It might have chile peppers from the farms of Mexico, feta cheese from the dairies of Greece, olive oil from the orchards of Italy, bamboo shoots from the communes of China and imitation bacon from the factories of America. Its ingredients have been known to number in the hundreds. It could be a first course, a main course, a snack and now a dessert.

You scoff? Look at Wendy's nearly 4,000 restaurants, with their 35-item salad bars. They've added chocolate pudding to the list. "This is the first concession on the salad bar for those of our customers with an unquenchable sweet tooth," explained Paul Raab, manager of corporate communications for Wendy's.

Such a move is not made lightly. Wendy's salad bars, like those of all such large-scale chain operations, are thoroughly thought out, with the tastes of the whole nation taken into account. Every salad bar throughout the country is set up according to a chart issued by the corporation, with regional and seasonal variations carefully computed into the plan.

Lettuce comes first on the lineup; that is the ingredient most used by people in their salads. Hard-cooked eggs and diced turkey ham are used least, said Raab, so they are in the least accessible spots -- the middle. Italian and French dressings are used more often than blue cheese and buttermilk, so the latter are positioned on the inside to leave the more convenient perimeter for the clear dressings.

Yet the considerations are even more complicated: Attractiveness also determines placement. So if the third row of crocks has white cauliflower in the back and white mushrooms in the front, the middle crock must have something with more color -- grated cheese.

Then there is chemistry. When eggs are placed near mushrooms, the mushrooms darken, so those two are kept well separated; nor are eggs placed where they might be spilled into mushrooms as they are spooned.

Salad bar theorists are sensitive to the boredom factor, too. Thus change is programmed in -- and growth occurs. Wendy's salad bars have increased from their original 20 items to 35 this year. In doing so, they have incorporated more prepared salads: coleslaw, red bliss potato salad, corn relish, four-bean salad (always trying to go everyone else one better), spiral pasta salad, chunky applesauce and something called "California-style fruit medley."

Therein lies the freedom of the individual entrepreneur. While the salad bar layout is dictated from the Dublin, Ohio, headquarters, eight of the crocks are allowed options. Rotating Crock No. 1, for instance could contain cottage cheese or creamy peppercorn dressing. The dressings in No. 2 could be celery seed, reduced-calorie bacon and tomato, or just lemon wedges. Rotating Crock Nos. 3 and 4 could include three-bean or four-bean salad, corn relish or pasta salad. And crocks 5 through 7 are allowed a dozen options, from sliced black olives to jalapenåo peppers to canned pineapple chunks to fresh watermelon. No. 8, the garnish crock, could offer sunflower seeds and raisins, chow mein noodles, saltine crackers or sesame crackers.

In all, the salad bar is a culinary sandbox for grownups (though children are of course allowed to play, too), carefully formulated for convenience, attractiveness and profit. And where the Reagan administration gave up trying to declare ketchup a vegetable in the school lunch program, Wendy's has managed to declare chocolate pudding a salad.

Tabletalk Wendy's claims to be the largest purveyor of chili in the world. In case you wondered why it would bother, here's a tip: That chili is made from leftover cooked hamburgers (no undercooked patties or patties with cheese or condiments allowed), boiled to kill any bacteria and to make the patties easier to chop. Next, I suppose, those salad bar leftovers will suggest that Wendy's add gazpacho to its menu.

The Italians have been defeated. No longer are Italian the most numerous of America's ethnic restaurants; Chinese have outnumbered them. In a three-year study of ethnic and regional restaurants using 271 telephone directories as sources, Pennsylvania State University geography professor Wilbur Zelinsky found more than 26,500 ethnic restaurants, about 10 percent of the total restaurants. While 7,796 were Chinese, 5,530 were Italian and 4,841 Mexican, the leading ethnic groups by far. Down at the bottom of the list were 12 Belgian, 11 Peruvian (three of them in the Washington area), and 7 Hawaiian.

San Francisco is going to have more than a taste of Mexico the weekend of Sept. 12-13. Its "Feria de la Bahia: A Taste of Mexico," originally scheduled for Sunday, Sept. 13, is moving to Saturday, Sept. 12, in order to leave plenty of room for the Mission District's annual 24th Street Fair, another look at Mexican food, music and crafts.

FAST CHOCOLATE PUDDING (4 servings)

Even faster than going to a fast-food restaurant for chocolate pudding is this blender marvel. It takes a day of chilling and thickening in the refrigerator, though, to reach its best thick, creamy texture.

1 cup light cream or half-and-half

6 ounces semisweet chocolate chips

1 egg

1 teaspoon vanilla, rum or Grand Marnier

Heat cream to scalding. Put chocolate chips, egg and vanilla in blender container, then pour in the hot cream. Blend until smooth. Pour into small dessert dishes and refrigerate for a day before serving.

1987, Washington Post Writers Group