As the daughter of the first Yugoslav Ambassador to Moscow, Kosara Gavrilovic learned many skills. She knows five languages, speaks them fluently, and is an expert at needlepoint. But she never learned to cook. Cooking was left to the family maids.

Only when she and her family left Yugoslavia during World War II and settled in England, did she begin to cook. Longing for native dishes, she began to watch Yugoslav cooks prepare meals and she quickly learned to stretch meager ingredients to create marvelous stews, peasant breads and vegetable and cheese pies. Even today Kosara still crumbles up dried, seemingly unusable pieces of phyllo to make perfectly good layers of dough.

Last fall she had a family "cook-in" at her Bethesda home, where she has created a grape-arbored open-air veranda and rock garden filled with plants from around the world. Those present, in addition to Kosara and her daughter Andjeliya Marcetic, were three sisters, including one visiting from Belgrade, and three nieces. Two days before the meeting Kosara had held a "staff meeting" to prepare for the luncheon, delegating shopping and preparation responsibilities to the various family members.

In Serbian fashion, guests were greeted with a sweet drink. Instead of the typical Slivovitz (plum brandy), however, Kosara had prepared a thick grape juice from the concord grapes hanging from her open-air veranda.

Since her kitchen is tiny, the cooks used the dining room to prepare several Yugoslav dishes. The pogaca (peasant) bread was prepared on the traditional wooden board placed on the floor instead of on a table. "This way I have more force for the kneading process," Kosara explained. The oval-shaped dough, covered with a crisscross design, was then placed directly on the grill to bake in a hot oven.

The other dish Kosara prepared was gibanica , a pie of cheese and flaky, many-layered pastry.The filling is usually made from aged-kajmak cheese. A good substitute is a mixture of feta and cream cheese.

The gibanica reflects the many influences on Serbia. Geographically at the crossroads of the East and the West, Serbian cooks chooses from either. The gibanica and its spinach-filled cousin zelyanica resemble Greek spanakopita and Albanian byrek . Yet these Serbian versions have a lighter, quiche-like quanlity more typical of the cuisine of Western Europe.

Both East and West flavored the entire meal, which was eaten on picnic tables in the rock garden. There was a cucumber soup wth yogurt, dill ad silvered blanched almonds. The crunchy pogaca bread was dipped in a spicy eggplant and green pepper "caviar." Bulgarians use mostly peppers in this preparation, the Russians use mostly eggplant. In Yugoslavia, Kosara explained, the proportions vary from household to household.

A zucchini salad had been tossed in a French dressing and mixed with hard-cooked eggs and dill. Then came grilled kebabs served with raw onions, Serbia's legacy from the Turkish horsemen and herdsmen. These were followed by a vegetable-laden Bosnian stew. A light orange peach sherbet ended the meal.

The following are several of Kosara's improvised Serbian recipes. POGACA Peasant Bread (Makes 1 loaf) 1 1/2 pounds self-rising flour 1/2 cup olive oil 1/2 teaspoon salt 1 cup plain carbonated water (about)

Combine all the ingredients, adding carbonated water until a soft dough is formed. Knead well. Add more flour if necessary. With a rolling pin spread the dough into a flat circle about 9 inches round and 1 1/2 inches thick. Sprinkle olive oil on both sides. Using a knife, make cuts about 1 inch apart crisscrossing the dough.

Place the dough directly on the center grill of a 400-degree oven and bake for about 45 minutes, or until golden. SERBIAN EGGPLANT AND PEPPER CAVIAR (8 to 10 servings) 10 green peppers 1/3 cup olive oil 1 large eggplant, punctured in several places with a fork 5 cloves crushed garlic, or to taste 2 tablespoons wine vinegar Salt and pepper to taste.

Rub the peppers with some of the olive oil and place in freezer while preheating the oven to 450 degrees. Place the peppers and eggplant in the oven and reduce temperature to 400 degrees. Roast until peppers collapse, about 20 minutes, then wrap peppers in a dish towel until cool. Continue to roast the eggplant until the skin is charred and the meat is soft.

Remove the skin from peppers and eggplant and chop finely. Add the garlic, olive oil, vinegar and salt and pepper to ttaste. Use as much oil as the vegetables will absorb. Place in a glass or ceramic bowl, chill and serve the next day. ZUCCHINI SALAD(6 to 8 servings) Juice of 1 lemon 1 teaspoon Dijon-style mustard 1/4 cup olive oil Salt and pepper to taste 1 pound zucchini 3 hard-cooked eggs 1 tablespoon fresh dill or to taste

Beat together the lemon, mustard, olive oil and salt and pepper. Set aside. Boil the whole zucchini about 10 minutes or until crunchy-tender. Cool and slice thinly. Remove the yolk from the eggs and mash with a fork. Finely slice the whites.

Combine the zucchini and eggs in a glass or ceramic bowl. Bathe in the salad dressing and sprinkle with the dill. Serve cold. This salad is best if prepared a day in advance. BOSANSKI LONAC Bosnian Casserole (8 to 10 servings) 2 pounds mixed meat cubes (beef, pork and lamb) 1/2 cup vegetable oil 8 small whole onions or 2 large onions 5 large garlic cloves, crushed 4 carrots, coarsely chopped 3 ribs celery, coarsely chopped 3 large tomatoes, coarsely chopped 2 tablespoons chopped fresh parsley 1 large potato, peeled and diced 2 tablespoons wine vinegar 2 cups white wine Salt to taste 12 peppercorns 1/2 cup flours Water

Brown meat in the vegetable oil. Arrange the meat and all the vegetables, including the garlic and parsley in layers in a deep earthenware pot or heavy casserole. Pour the vinegar and wine over, adding the salt to taste and the peppercorns. Add enough water to the flour to be able to make a thick paste. Form into a long strip and attach the dough to the rim and lid of the casserole. Seal lid to casserole. Place the pot in a 300-degree oven and simmer a good four hours.

This stew is best prepared a day in advance and reheated.

Note: If the taste is too vinegary at the end, add a touch of baking soda to the stew. GIBANICA Crusty Cheese Souffle Pie (8 to 10 servings) 1/2 pound phyllo dough 3/4 cup unsalted butter 1 pound feta cheese 6 ounces cream cheese 5 eggs 1/2 cup vegetable oil and water

Remove phyllo dough from refrigerator before beginning the recipe. Rub 1//4 cup of the butter into a deep, heavy 2-or 3-quart casserole with a lid. Use a potato masher to break up the feta and combine with the cream cheese. Add the eggs to the cheeses, mixing well with a beater after each addition. Stir well until thick and creamy.

Spread 4 or 5 sheets of phyllo into the casserole one at a time. It does not matter if they do not fit exactly or if they crumble. After placing each sheet, sprinkle with mixture of oil and water. Place about 1 1/2 cups filling in the casserole. Cover with three leaves of phyllo, sprinkling with oil and water. Repeat with filling and leaves until all the filling is used up. The casserole should be about 3/4 filled. Cover with another three or four leaves and sprinkle with oil and water. Melt the remaining 1/2 cup butter and pour over the leaves.

Bake in a 400-degree oven about 45 minutes. The gibanica is done when the crust is golden brown and a knife comes out clean when inserted in the crust. Remove from oven. Insert a spatula around the crust to make sure the sides do not stick. Carry casserole to the sink, place the cover on top and flip over. The bottom crust will now be the top. Transfer to a plate or platter and serve.

Variation: To make a zelyanica (spinach cheese pie) use the above ingredients and add to them one 10-ounce package of frozen chopped spinach, defrosted and the water squeezed out, plus a handful of chopped fresh dill with stalks. Proceed as for the gibanica.