WHEN IT comes to a well-planned outdoor meal, you can take it with you. That's what a picnic is all about. Besides being portable, picnic fare should be able to withstand the typical jostling it receives as finicky picnickers search for the perfect glade.

But the food that is chosen shouldn't wither from the weather.

Finally, it's a good idea to choose dishes that are easily made in advance. Although some diehards might prefer to drag along the hibachi and the charcoal and the lighter fluid, even they will have to agree it's more relaxing to sit down in the open air and simply unwrap all the scrumptious food.

The following meal takes this into consideration -- It will serve six people with average appetites. MENU

Rainbow Fruit Medley, Greek Salata in Pita Bread, Sesame Oven-Fried Chicken, Herbed White Beans, Lemon-Berry Cake Squares, White Wine Fruit Punch. RAINBOW FRUIT MEDLEY 2 cups fresh watermelon balls or cubes 1 cup fresh cantaloupe balls or cubes 1 cup canned pineapple chunks, drained 1/2 cup fresh seedless grapes, washed and sorted 1/2 cup blueberries, washed and sorted 1 package (10 ounces) frozen raspberries, thawed and drained or 1 cup fresh (optional)

Combine all ingredients in a large plastic refrigerator carton or bowl with cover. Stir carefully to mix. Store in refrigerator up to one day. Pack in ice chest for picnic. GREEK SALATA IN PITA BREAD 6 to 8 large lettuce leaves, romaine or iceberg 4 to 6 radishes 1/2 of each, medium green pepper, red onion and cucumber 6 cherry tomatoes, cut in half or 2 medium tomatoes, cut in wedges 12 (or more) Greek olives or plain ripe olives 6 ounces Feta cheese, broken into small chunks 1 to 2 teaspoons fresh or 1/2 to 1 teaspoon dry dill seed (to taste) 1/4 cup olive oil 1 1/2 tablespoons wine vinegar 6 small pita breads

Carefully clean lettuce, radishes, green pepper, red onion and cucumber. Drain well. Slice these vegetables very thinly (the Greeks prefer even the lettuce sliced) and place in a medium bowl that has a cover. Add tomatoes, olives and Feta cheese. Sprinkle dill on top. Gently toss salad and cover. In a small jar, mix oil and vinegar for dressing and reserve.

Salad can be made several hours ahead and stored in refrigerator. To prepare pita bread, cut a thin slice from the top of each one (to form pocket). Then wrap breads tightly. At picnic time, toss salad with dressing; then stuff into pockets. SESAME OVEN-FRIED CHICKEN 15 saltine crackers (or similar whole wheat crackers) 1/4 cup sesame seeds 1/2 teaspoon paprika 1/2 teaspoon salt (optional) 1/4 cup evaporated milk (or 3 tablespoons nonfat dry milk dissolved in 1/4 cup water) 1 broiler-fryer chicken (3 pounds), cut into pieces and skinned 6 to 8 tablespoons butter or margarine, melted

Place crackers in blender or food processor or crush by hand into fine crumbs. (You should have about 1 1/4 cups.) Add sesame seeds, paprika and salt (if desired) to make a coating mix.

Dip chicken pieces into milk; then roll in crumbs to coat well. Allow coated pieces to rest about five minutes for coating to dry.

Pour melted butter or margarine into the bottom of a baking pan (preferably non-stick) large enough to hold all of the chicken. Roll each piece in the melted butter or margarine as it is placed in the pan. Bake uncovered at 375 degrees for one hour. Chill completely. For picnic, wrap well and place in ice chest. Chicken may be prepared one day ahead and refrigerated. (Or freeze for longer storage, and pack while still slightly frozen). HERBED WHITE BEANS 2 cups dry navy beans 1/3 cup chopped scallions 1/2 cup chopped fresh parsley 2 ribs celery, chopped 1/4 cup salad oil 3 tablespoons white wine vinegar Dash pepper 1/2 teaspoon salt 1/8 teaspoon dry mustard 1/4 teaspoon dried basil or 1 teaspoon fresh 1 teaspoon sugar

Rinse dry beans well. Place in a saucepan and cover with about two inches of water. Bring to boil, cover and simmer for about 1 1/2 to 2 hours or until tender. Add more water, if necessary, during cooking. Drain cooked beans; then cool slightly. Gently toss in scallions, parsley and celery. Put remaining ingredients into a small jar and shake to mix well. Pour over beans and gently mix in. Chill beans well. Store in a covered container in the refrigerator. May be made up to three days ahead. LEMON-BERRY CAKE SQUARES 1/3 cup milk 1 teaspoon lemon juice 1/4 cup butter or margarine 1/2 cup sugar Peel of one lemon (yellow part only) 1 large egg 1 1/2 cups whole wheat pastry flour, or all-purpose flour 2 teaspoons baking powder 1/4 teaspoon salt 2 cups blueberries, raspberries or blackberries Glaze: 2 tablespoons butter, melted 2 tablespoons brown sugar Juice of one lemon (about 2 to 3 tablespoons)

Mix milk and 1 teaspoon lemon juice. Set aside. Cream softened butter with sugar. Mix in grated lemon peel and egg. Mix in milk alternately with remaining dry ingredients, being careful not to overmix batter.(Mix just enough to combine ingredients. Batter will be very thick.) Carefully fold in berries. Evenly spread batter in a well-greased 8-inch square pan. Bake in a preheated 350-degree oven for 40 to 45 minutes, or until cake tests done.

When cake is almost done, combine all glaze ingredients. When cake is done, spread this mixture over the top. Then place cake under broiler for a minute or two until glaze is bubbly. Cool cake in pan. Cut into squares, but leave in pan for ease in transporting to picnic. Store cake at room temperature for up to two days, or freeze for longer storage.

(Note: This cake is made very quickly in a food processor. Mix milk and lemon juice as above. Place cold butter, cut into pieces, into bowl fitted with steel blade. Add sugar and lemon peel cut into large squares (not grated). Process about 20 seconds to cream butter and sugar and to grate peel. Add egg and milk through chute while processor is running. Turn off machine. Add flour, baking powder and salt. Process very briefly in pulses; just enough to mix. Remove knife from bowl and fold in berries. Then proceed as above). WHITE WINE FRUIT PUNCH 3 cups white jug wine, such as sauterne 3/4 cup lemon juice 3/4 cup orange juice 1 1/2 cups pineapple juice 1 to 1 1/2 cups sugar, to taste 1 bottle (28 ounces) club soda

Mix all ingredients except club soda, and chill. This can be done ahead. (Note: Some of this mixture may be poured into an ice cube tray and frozen to later keep punch cold without diluting it). When ready to pour into picnic jug, mix club soda with wine-juice mixture (and add special frozen cubes, if desired).