It's no surprise that the carrot, rich in fiber and vitamin A, is a healthful, low-calorie vegetable. (An average carrot contains only about 20 calories.) That's why raw carrots are a familiar snack for dieters, as well as a popular salad ingredient.

But what might surprise you is that cooked carrots are more nutritious than raw ones. When sliced or grated carrots are cooked, some of the fiber is destroyed, but cooking releases the vitamin A that is tightly held in cellulose cells. Taking advantage of this nutritional bonus is easy, since carrots figure in a wide and tempting variety of cooked dishes, from appetizers to casseroles to desserts. Their mild flavorblends nicely with other foods, and they add moisture to baked goods.

Unlike many seasonal vegetables, carrots are available in abundance throughout the year. Although local gardeners often grow a large supply, most carrots sold in area stores come from California, Florida and even Michigan. When buying carrots, select those with a firm texture, and check for a deep-orange color, which insures a higher vitamin A content and rich flavor.

Raw carrots on the relish tray or hors d'oeuvre platter may never go out of style. If, however, you're looking for new ways to cook with carrots, here are some reciipes. DILLED CARROTS

(6 appetizer servings; 4 side dish servings) 6 large carrots 1/2 cup apple cider vinegar 1/2 cup water 1 tablespoon fresh dill, or 1 1/2 teaspoons dried dill 1 teaspoon seasoned salt

Several hours before serving, slice carrots one-half inch thick, holding knife at a 45-degree angle to form large oval discs. Place carrots in saucepan with remaining ingredients, and bring to boiling. Lower heat, and simmer 10 minutes longer. Carrots should still be slightly firm. Transfer carrots and cooking liquid to large jar, and refrigerate several hours or overnight. Drain off marinade before serving. A good recipe for dieters. CREAM OF CARROT SOUP

(4 servings) 1 pound carrots, thinly sliced 1 small onion, finely chopped 4 tablespoons butter or margarine 1/3 cup water 1/2 teaspoon sugar 1 teaspoon salt Dash of freshly ground pepper 2 tablespoons flour 3 cups milk Dash of nutmeg 1 tablespoon fresh lemon juice

In large saucepan, combine carrots, onion, 2 tablespoons of butter, water, sugar salt and pepper. Place over low heat, cover, and cook 25 to 30 minutes, or until carrots are tender. Puree mixture in blender, one-third at a time, until very smooth. In another saucepan, melt remaining butter over low heat, and blend in flour, mixing until smooth. Cook, stirring constantly, 5 minutes. Add milk and nutmeg, and continue cooking, stirring constantly, until mixture is slightly thickened. Stir in carrot mixture, and continue cooking, covered, 30 minutes. Stir occasionally. Just before serving, add lemon juice. Serve hot, garnished with freshly grated parsley or chopped watercress, if desired. CARROT AND APPLE TSIMMES

(6 to 8 servings) 4 cup grated carrots 1 tablespoon barley 2 apples, peeled and grated 3tablespoons butter or margarine 1/2 cup water 1/2 teaspoon salt 2 teaspoons sugar 1/4 teaspoon nutmeg

Combine all ingredients in a large saucepan. Cover, and cook over low heat for 2 hours, or until barley is soft. Check every half hour to make sure there is enough liquid in bottom of pan. If necessary, add a little more water - about 1/4 cup is sufficient. Serve hot.

Tsimmes is a dish of Jewish origin traditionally served at festive meals during Rosh Hashanah and Passover. BAKED CARROT RING

(8 to 10 servings) 3/4 cup shortening 2 eggs, separated 1/2 cup brown sugar 1 teaspoon lemon juice 1 tablespoon cold water 1 1/2 cups grated carrots 1 cup flour 1/2 teaspoon baking soda 1 teaspoon baking powder 1/2 teaspoon salt 1/2 cup bread crumbs

In large bowl, with electric mixer at medium speed, cream shortening, egg yolks and brown sugar, beating until smooth and fluffy. Add lemon juice, water and carrots, blending well. Sift flour, baking soda, baking powder and salt together, and add to carrot mixture. Wash beaters well and in another bowl beat egg whites until stiff. Fold into batter until thoroughly incorporated.

Grease a 9-inch ring pan, and sprinkle with bread crumbs to form a thin coating. Spoon batter into prepared pan, and bake in preheated 375-degree oven 40 to 45 minutes, or until nicely brown on top. Let cool in pan on wire rack 5 minutes. To serve, unmold onto large platter.

This may be served as a dessert or as a side dish. In the latter case, you can fill the center of the ring with a mixture of cooked peas and sliced mushrooms.