PIE--THE symbol of America. What with baseball strikes and professional mobility (so Mom means Ma Bell), apple pie may be the only constant any more.

But what of this dish, apple pie? The U.S. Department of Agriculture estimates that a piece weighs in at 345 calories; pecan pies even more. That's a hefty dessert for an already hearty holiday meal replete with gravy and dressing and candied sweet potatoes.

Which is not to say it's time to do without. Indeed, if one does without Mom and baseball, one needs a pie -- and not just dessert pie, either, but vegetable and main dish, too.

All manner of pies can fit the new American consciousness. The same people who are interested in diet beer and light wine, whole wheat bread or low cholesterol cheeses might be interested, too, in contemporary pies. As pies once represented America, so they still do, in a more healthful form -- quiches without cream, pie crust without cholesterol and main dish pies without meat. Calories have been cut; saturated fat has been trimmed.

This idea has been captured in a booklet published by the Cornell University Cooperative Extension service. "Contemporary Pies" attempts to instruct the piemaker in the basics of whole-wheat pastry, slim-line quiche, complementary-protein pies, vegetable pies and dessert pies.

While the booklet is a slim $3 worth, offering little more than handy tips in its 20 pages, it does introduce some provocative cooking techniques that could easily be adopted by cooks interested in improving the diet of their families.

* Pie pastry, made partly with whole wheat flour, can use margarine or oil in place of butter and shortening (high in saturated fat).

* Quiche recipes are adapted to low-fat milk and reduced-calorie cheeses.

* In meatless pies, vegetables can create a combination of complementary proteins. One recipe calls for cornbread and beans with just a little cheese; another calls for beans, rice and cheese.

* The booklet advises a diet emphasizing vegetables rich in vitamins A and C, adding that these foods are typically low in calories. Warning against destroying vitamins during cooking, it directs how to stir-fry or steam vegetables to retain their nutrients.

Pointers are given on reducing the amount of calories in dessert pies by making one-crust pies rather than pies with a top crust (replace the top crust with a light sprinkling of spicy crumbs); by selecting fruit pies that can be made naturally low in sugar (such as apple), and by serving smaller portions attractively garnished. WHOLE WHEAT PIE CRUST (Makes 2 9-inch crusts) 1 cup whole wheat flour 1 cup white flour 1 teaspoon salt 2/3 cup margarine 6 tablespoons ice water Combine flours and salt. With pastry cutter, 2 knives or a food processor, cut margarine into flour until it resembles meal. Sprinkle with a little water, toss lightly, and sprinkle with a little more water.

Whole wheat pastry is, by nature, a little tougher than regular white pastry (because of higher gluten content in whole wheat flour). If possible, get whole wheat pastry flour from a health food store to make pie pastry (and other baked items). Avoid overworking the pastry, which will make it tougher. Also, whole wheat flour takes longer to absorb water, and may take a little more water than regular pastry. It's more important, then, that the pastry be given time to rest (preferably in the refrigerator).

When the water has been added and the pastry will hold together in a ball, chill it briefly. Sprinkle a countertop lightly with flour. Place one ball on top of the flour and press it down. Coat a rolling pin with flour and lightly dust the top of the pastry with flour. Roll in all directions from the center. Flip the pastry, lightly dust the top side and roll again until the pastry is about 1/8-inch thick. Roll it lightly around the rolling pin and unroll it over the pie plate. Press it gently into the plate and trim the sides. Do not expect the edges to be as pliable as regular pie pastry.

For most pies, you may want to brush the shell with beaten egg white or whole egg and bake for 5 minutes at 350 degrees. SPINACH QUICHE (Makes a 9-inch quiche) 2 tablespoons vegetable oil 3/4 cup chopped mushrooms 1 medium onion, chopped 1/2 teaspoon oregano 1 quart chopped fresh spinach (or 1 package frozen) 2 eggs 1 cup evaporated skim milk 1/4 teaspoon salt 1/2 cup grated provolone cheese 1/2 cup skim-milk ricotta or farmer's cheese

Heat oil in skillet. Add mushrooms, onion and oregano and cook until mushrooms have given up their liquid and shrink. Add spinach and cook until all the liquid has evaporated. Remove from heat. Beat eggs in a large bowl. Still beating, add milk and salt. Stir in cheeses. Add spinach mixture. Stir to combine and pour into partially cooked whole wheat pie shell. Bake at 375 degrees for 40 minutes. Allow to sit 10 minutes before serving. BEANS AND CORNBREAD PIE (Makes an 8-inch square pie) 2 1-pound cans pinto or kidney beans, drained (save some of the liquid) 3 tablespoons vegetable oil 1 medium onion, chopped 2 cloves garlic, minced 1 green pepper, minced 1/2 cup chopped celery 1/4 cup minced parsley 1 teaspoon chili powder 1/2 teaspoon salt 1 tablespoon ketchup 1 cup corn kernels 1/2 cup cornmeal 1/2 cup flour 2 teaspoons baking powder 1/2 cup skim milk 1/4 cup grated cheddar cheese Mash 1 can of beans and set aside. Heat 1 tablespoon oil in a large skillet and add onion and garlic. Cook over medium heat about 5 minutes. Add green pepper, celery and parsley and cook 5 minutes more. Add all the beans, chili powder, 1/4 teaspoon salt, ketchup, corn kernels and 3 tablespoons of the liquid from the beans. Cook over low heat as you make cornbread.

Combine cornmeal, flour and baking powder in a small bowl. Add skim milk and 2 tablespoons oil. Stir lightly to combine. Pour 2/3 of the mixture into a lightly greased 8-inch square baking pan. Top with bean mixture. Do your best to spread the remaining cornbread mixture over the beans (this isn't terribly easy -- it'll be sort of dumpling style). Sprinkle with cheese. Bake in a 350-degree oven for 30 minutes.

Contemporary Pies" is a 20-page booklet published by the Cornell University Cooperative Extension. To obtain a copy, send your name, address and $3 to: Distribution Center-WP, 7 Research Park, Cornell University, Ithaca, NY 14850.