NOT ALL PICNICS are for baskets. There are picnics for backpacks and picnics for saddle bags, picnics to stuff in purses or briefcases. A carefully chosen picnic can be carried on a bike or wrapped in a towel with your bathing suit.

This week's menu can serve as a picnic that is not a project--an easy-to-carry all-in-one lunch. It is a sandwich with no mess, nothing to leak or slide or come apart. And it can be made ahead and stored in the refrigerator or freezer in case a sunny day should coincide with the weekend.

It calls for biscuit dough. Obviously that can be bought in the supermarket ready to roll. But just in case your shelf already holds the extra staples--yeast, baking soda and powder, buttermilk or regular milk and vinegar--and you are willing to spend a few more minutes stirring up your own, a recipe for biscuits is included. This recipe is easy and takes little time to mix, but it rests in the refrigerator overnight or longer, at which time it becomes as handy as that roll of refrigerated biscuit dough you might have bought. If you have even less time or inclination to spend in the kitchen, the filling alone is a good sandwich spread.

In addition to a sunny day, this pick-up picnic requires that you have on your shelf the usual flour, sugar, salt, pepper and shortening, at least if you are making your own biscuits.

EXPRESS LANE LIST: chicken or tuna, cheddar cheese, celery, onion, curry powder, mayonnaise, biscuit dough (or yeast, buttermilk or milk and vinegar, baking powder, baking soda). CHICKEN OR TUNA TURNOVERS (Makes about 24 turnovers) 4 cups finely chopped cooked chicken or tuna 1 1/2 cups shredded cheddar cheese 2 stalks celery, chopped 1 medium onion, finely chopped 2 teaspoons curry powder 1/2 cup mayonnaise Salt and pepper to taste Biscuit dough for 24 biscuits (see recipe below)

Combine filling ingredients and set aside. On a lightly floured board roll dough 1/8- to 1/4-inch thick and cut into 6-inch rounds or squares. Put about 1/4 cup filling on each round, fold over and seal. Arrange on baking sheets, leaving room for turnovers to rise and spread. Bake at 425 degrees for 12 minutes or until browned. Remove from pan and let cool. Serve at room temperature. READY-WHEN-YOU-ARE BISCUITS (Makes about 3 dozen biscuits or 2 dozen turnovers) 1 package yeast 2 tablespoons warm water 2 cups buttermilk (or 2 cups milk mixed with 2 tablespoons vinegar) 3 tablespoons sugar 1 teaspoon salt 5 cups flour 1 tablespoon baking powder 1 teaspoon baking soda 3/4 cup shortening

In a large bowl dissolve yeast in water. Add buttermilk, sugar and salt, and set aside. In another bowl combine flour, baking powder and soda, then cut in shortening until it resembles small peas. Add liquid ingredients and mix lightly but do not knead the dough. Refrigerate overnight or up to three days.

When ready to bake, pinch off amount of dough needed and return the rest to the refrigerator. Knead the dough, roll out on a lightly floured board (do not allow it to rise), cut and bake at 425 degrees for 12 minutes.