IT USED TO BE that the grandest dream was to see Independence Day's climax from a rooftop, and every such spot in town was booked long ahead. Now we think bigger--higher, anyway. We imagine what it would be like seen from a satellite. Gaze on all of America, every burg, hamlet and metropolis of it, lit up like--well, like the Fourth of July.

We would see entire populations of small midwestern towns lying flat on their backs in public parks, letting fireworks soot drift down onto their clothes. We would see boats bobbing in fireworks-lit bays, and American flags sputtering and smoking into shape near the ground while everybody claps and cheers and starts packing to go home.

And glinting and sparkling beneath the light of the fireworks would be countless yards of aluminum foil being ripped open by Fourth of July picnickers from Maine to Hawaii. How many chickens, how many ribs? How many Tupperware bowls being snapped open to reveal Mom's creamy potato salad? How many coolers collapsing under the strain of too many six packs, too much coleslaw?

Washington's town square is the Mall, which on the night of the Fourth is several square miles of oohing, aahing faces lit in red, white and blue. But we have bays and marinas, too, for fireworks viewing, as well as downtown rooftops and secret hillsides and all the balconies of northern Virginia.

The king of all our parks, Secretary of Interior James Watt, already has decided where he'll set up his blanket and cooler, and what he'll eat, too. Actually Watt won't need a blanket. He's invited a couple hundred people--mostly staff members and their families--to drop by his Interior Department office to share some of the "good basic American foods" Watt likes best.

Watt spokesman Doug Baldwin was willing to share the menu: hamburgers, hot dogs, potato chips, fresh popcorn from a popcorn maker installed on the premises, soft drinks and cold cuts. "Some of the wives bring along homemade cookies, rolls and breads," according to Baldwin.

Watt, who lighted some sparklers of his own by announcing that the Beach Boys shouldn't be invited to our national birthday party and Wayne Newton should, won't be able to hear singer Newton's 6 p.m. Sylvan Theater performance from his office. But he will have a great view of the fireworks.

Other Washingtonians, and tourists, will have to set up camp early to get a good spot. Joe Geary, a spokesman for the National Park Service's National Capital Region, says, "You can almost tell how long people have lived in the Washington area by how early they get there" to set up on the Fourth of July. Really old-timers, Geary says, seem to like East Potomac Park best, and they arrive early in the morning. They set up lawn chairs and grills and spend the day schmoozing and eating, then wander over to the monument grounds later for a better view of the fireworks.

The Fourth of July brings out a great crowd, says Geary, who every year is offered more than he can eat from picnic baskets all up and down the Mall. The chief maintenance man in the mall area, William Newman, and his crews haul off between 80 and 85 tons of chicken bones, aluminum foil, fried chicken buckets, dead charcoal grills and broken lawn chairs after every Fourth, but still Joe Geary says, "One of the things I'm consistently impressed by is how clean the parks are afterwards." The people make an effort to get trash in the trash baskets, Geary says, but the crows are really a pain. They pick up the trash again and fly it all over town.

Picnic baskets, of course, can be anything from grocery bags to English wicker hampers. And they can contain potato chips or smoked pheasant. What you cart off to the fireworks depends partly on where you're going to park your picnic basket. Picnicking on the Mall requires a meal that can be packed vertically instead of horizontally, since your own little corner will be just slightly larger than a postage stamp.

If you're watching the fireworks from a boat you don't want sloshy stuff, but if you're lucky enough have access to an office rooftop you really can spread out.

The recipes that follow can be mixed and matched to suit your location. The cold lamb can be tucked into the flat bread if you need to be efficient with space, left to be served separately if you have more room to spread out. If you have children who might not like lamb, peanut butter isn't bad on flat bread either. The cold soup is most suitable for a rooftop or a balcony, and Mom's potato salad is good anywhere, anytime. If you're feeling particularly patriotic, the raspberry champagne provides the red, the blueberry turnovers the blue.

All of this can be made well ahead of time, most of it the day before. The mayonnaise should be added to the potato salad at the very last minute and the whole kept cold. An even better idea would be to pack the mayonnaise separately in a thermos and add it at the picnic site. Foods like mayonnaise that contain raw eggs are especially susceptible to spoilage. COLD CUCUMBER-WATERCRESS SOUP (6 servings) 2 tablespoons butter 4 medium cucumbers, peeled, seeded and chopped roughly 4 scallions, chopped 1 medium potato, peeled and chopped roughly 1 bunch watercress, leaves only 2 1/2 cups chicken broth Salt and pepper 1/2 cup heavy cream Chopped fresh herbs to taste

Melt butter in a heavy saucepan over medium heat. Add cucumbers and scallions and let cook slowly for about 10 minutes, until softened. Add potato, watercress, chicken broth and salt and pepper. Simmer partially covered for about half an hour, until all is soft. Pure'e in a food mill or food processor and let cool. If soup seems too thick when cool, add more broth or water. When cold, add heavy cream and correct seasoning. Chopped fresh herbs can be added at serving time. (Chervil is especially nice.) POCKET BREAD (Makes 12 pieces) 1 package yeast 1 cup warm water 1 teaspoon salt 1 tablespoon vegetable oil 2 1/2 to 3 cups flour

In a large mixing bowl, dissolve yeast in warm water. Add salt, oil and 1 cup of flour, stirring to blend. Gradually add enough flour to make a fairly soft dough. Knead on a floured board for about 8 minutes, until dough is smooth and elastic. Put dough in an oiled bowl, turning to coat all sides, and let rise, covered with a dish towel, until double in bulk, about 1 hour.

Punch dough down and divide into twelve equal-sized balls. On a well-floured board, flatten balls with rolling pin to even circles about five inches in diameter. Transfer disks to ungreased cookie sheets and let them rise, covered, until they look puffy, about half an hour.

Preheat oven to its highest setting. Bake for 5 to 8 minutes, depending on how hot the oven is. Breads will be puffed and just slightly browned in places, and will have a natural pocket. Cover with a kitchen towel and let cool.

To use as sandwich bread, cut in half and put filling in natural pocket. HERBED LEG OF LAMB (8 to 10 servings) 1 boned leg of lamb, about 5 pounds 4 cloves garlic 1/2 cup parsley 3 tablespoons olive oil Salt and pepper to taste

Ask the butcher to bone the leg of lamb but not tie it up. Ask him for enough string to tie it after you've spread the inside with the garlic-parsley mixture.

Chop the garlic and parsley together until fine, then add the olive oil and salt and pepper. Spread half this mixture on all the inside surfaces of the lamb. Tie the lamb into approximately the same form it had when the bone was still there. (It will not look great at this point, but you will be serving it already sliced.)

Roast the lamb for 1 hour at 350 degrees. Remove lamb from oven and spread with the remaining garlic-parsley mixture, then return to oven and roast until lamb is medium rare, about 30 minutes. Let lamb cool, then refrigerate. (Uncooked bones and roasting juices can be frozen and saved for a future lamb stock.)

Serve cold, sliced, with caper mayonnaise (recipe follows). CAPER MAYONNAISE (Makes 1 cup) 1 cup mayonnaise, preferably homemade 2 teaspoons dijon mustard 2 tablespoons capers, drained

Mix all together and keep very cold until serving time. Serve with lamb. MARINATED VEGETABLE SALAD (6 servings) For the dressing: 1 clove garlic 1 tablespoon parsley 1 teaspoon dijon mustard 3 tablespoons white wine vinegar Salt and pepper to taste 1/2 cup olive oil For the salad: 1 head cauliflower 1 bunch broccoli (about 1 1/2 pounds) 1 medium zucchini 1 medium yellow squash 1/4 pound mushrooms 1 pint cherry tomatoes 2 scallions, chopped Chopped fresh herbs to taste (optional)

Make dressing: If you have a food processor, all ingredients can be put in work bowl at once and processed. If you are working by hand, mince garlic and parsley together, then add mustard and vinegar and whisk. Add oil slowly, whisking. Correct seasoning.

Since the marinade for this salad will continue to "cook" the vegetables, their initial cooking should be just long enough to make them barely tender and still a little crisp.

Divide cauliflower and broccoli into bite-sized florets. (Save stems for soup.) Cook separately in boiling salted water, cauliflower for about three minutes, broccoli about two minutes. Drain thoroughly, then pat dry with paper towels. Slice unpeeled zucchini and yellow squash evenly and cook in boiling salted water for about 30 seconds. Drain and pat dry.

Slice mushrooms and add raw to other vegetables. If cherry tomatoes are large, cut them in half and add. Mix in minced scallions and optional herbs, then add dressing and toss carefully.

Let salad marinate a few hours or overnight. MOM'S POTATO SALAD (6 servings) 5 or 6 medium potatoes (3 3/4 to 4 cups when cubed) 3/8 cup bottled Italian dressing or your own mixture of vinegar, oil and seasoning 3 hard-cooked eggs, chopped 1/4 cup finely minced onion 1 cup diced cucumber 1 cup chopped celery Salt and pepper to taste 1/4 teaspoon paprika Mayonnaise to taste

In a saucepan, cover unpeeled potatoes with cold water, then cook over medium heat until just tender when pierced with the point of a knife. Don't try to use leftover, cold potatoes for this salad, as they won't absorb flavors. Idaho potatoes seem to absorb dressing better.

Peel and dice potatoes while they're still warm, and immediately toss gently with italian dressing. Refrigerate when cool, and let marinate several hours or overnight.

Meanwhile, mix eggs, onion, cucumber and celery. At least an hour before you're ready to serve, toss egg mixture with potatoes, add salt, pepper and paprika to taste, then refrigerate. This mixture needs at least an hour to blend flavors.

Just before serving time, toss with enough mayonnaise to bind.

Additional possibilities for garnishes include olives, pickles, chopped green pepper, grated carrot and pimiento. BLUEBERRY TURNOVERS (Makes 18 turnovers) 17 1/4-ounce package frozen puff pastry dough 2 cups blueberries, washed and picked over for stems and leaves 1/2 cup sugar 1 1/2 tablespoons cornstarch Few drops lemon juice Few gratings of fresh nutmeg 1 egg yolk Granulated sugar

Remove puff pastry from freezer about 20 minutes before you intend to use it.

Mix blueberries with sugar, cornstarch, lemon juice and nutmeg. If blueberries seem a little flavorless, add more drops of lemon juice.

Roll each square of puff pastry to a 12-inch square. With a sharp knife, cut each square into nine 4-inch squares. Place a spoonful of blueberry mixture in the center of each square. Moisten two adjacent edges of each square, then fold each square corner-to-corner around the blueberry mixture to make a triangle. Press together with fingertips, then with the tines of a fork. If edges aren't sealed well, filling will leak.

Mix egg yolk with two teaspoons of water. Brush surface of each turnover with egg mixture, taking care not to let it run down sides or pastry won't rise in oven. Sprinkle tops with a little granulated sugar, and bake in a 400-degree oven for about 25 minutes, or until puffed and brown. RASPBERRY CHAMPAGNE (1 serving) Raspberry liqueur (framboise) Champagne

Pour a tablespoon (or to taste) of liqueur in each glass, then fill with champagne.