IF THERE is one place worse in summer than Washington, it's Manhattan. But my friends there have refined coping to an art, which includes cookouts in the city.

One hot day, we took the kids across Riverside Drive for a picnic in the park along the Hudson River, weaving our way through boys playing ball and young men who rode with one hand on the handlebars of their bikes and the other holding a transistor radio. The hibachi followed behind us in a red wagon.

In the wagon, along with the hibachi, we'd packed a soup bowl and a pair of chopsticks for each person. When we ate, the flavors blended in the single bowl, more convenient than a floppy paper plate for eating on the grass. We also brought chilled white wine and paper cups. Jeff, the cook, having passed through the wine connoisseur stage, does not stand on ceremony, and sometimes serves a fine vintage in jelly glasses.

We found a secluded tree, and in its shade, Jeff orchestrated an oriental barbecue. This is my version of it, developed back home. The only thing I haven't tried making is the dessert, which was popsicles we bought from an ice cream man.

Since everything is marinated in some way or another, it can all be done ahead except for the grilling. In fact, everything including the cold rice and vegetables can be done before work in the morning. COLD RICE (4 servings) 3 1/2 cups cooked rice 2 tablespoons rice vinegar

While the rice is still hot, spoon it into a plastic container and sprinkle the vinegar over it, then toss lightly with a fork. Allow to cool uncovered, then refrigerate. Rice vinegar is available from Oriental markets or plain white vinegar can be substituted. TOMATO-CUCUMBER SALAD (4 servings) 2 cucumbers 4 tomatoes 2 tablespoons sesame oil 2 tablespoons red wine vinegar

Salt and freshly ground black pepper to taste

Peel the cucumbers, and seed and juice the tomatoes. Then cut them into small bite-size chunks and put them in a bowl. Add the sesame oil and the vinegar, and toss together. Season to taste. Let sit for at least half an hour. SKEWERED LEMON CHICKEN (4 servings) 4 boneless chicken breasts 1 tablespoon grated lemon rind 1 or 2 large cloves garlic, minced 3 tablespoons soy sauce 3 tablespoons dry white wine 2 tablespoons peanut oil or vegetable oil 2 green peppers 8-ounce can whole water chestnuts

Rinse the chicken, pat it dry with paper towels and cut it in 1 1/2- to 2-inch cubes. Combine lemon rind, garlic, soy sauce, wine and oil in a non-metallic bowl, and add the chicken. Marinate for at least half an hour. Cut the green peppers into 2-inch chunks. Alternate the water chestnuts, chicken and green peppers on 12 6-inch skewers.

When the coals in the hibachi are half gray, put the chicken kebabs on the grills, 2 or 3 inches from the heat, turning the kebabs until nicely browned. They will start being done in about 15 minutes. Serve them as they finish, and do not overcook, or the chicken will dry out. Then, while your guests eat the chicken, broil the beef. BEEF TERIYAKI (4 servings) 1 to 1 1/2 pounds round steak 4 chopped scallions, including the green 2 tablespoons fresh ginger, thinly sliced 1/2 cup thin soy sauce ( 1/3 cup if using Kikkoman) 2 teaspoons sugar 1/2 cup dry white wine 3 tablespoons peanut oil or vegetable oil Freshly ground black pepper to taste

Pat the meat dry with a paper towel. Trim off the fat, and score the meat in a crosshatch pattern. Combine the remaining ingredients in a flat, non-metallic baking dish. Add the meat, spooning the marinade over it. Marinate for several hours.

After the chicken is done, lower the grills of the hibachi to about 1 inch from the coals. Put on the beef, turning and basting it every 3 minutes. Medium rare takes a total of 6 minutes a side. Put the beef on a serving platter, and with a sharp knife, slice very thinly across the grain, as for london broil.