BY NOW, if you have tried any of the 30-minute meals that we have published, you are, perhaps, a believer. For those who haven't, 30 minutes means 30 minutes from the time you don an apron until the moment that you sit down at the table.

It does not include shopping for the very few groceries you will need and it doesn't include washing the dishes. But there aren't many of them, either. In fact, some of the meals are so simple to prepare that they take less than 30 minutes.

This quick meal will fit in with almost any sensible low-calorie diet plan, but it tastes so good no one is likely to think of it as low-cal food: Chinese broiled fish, steamed asparagus and green salad with yogurt-grapefruit dressing. For the heartier eater it's easy to add some crusty sourdough rolls and sweet butter.

Choose strawberries for dessert whether you are dieting or not. To keep them low calorie, spoon on some orange juice. For a few more calories, spoon on a little kirsch or orange-flavored liqueur.

The menu is for two people but can be doubled easily to serve four. 30-MINUTE MENU FOR TWO Chinese broiled fish* Steamed Asparagus* Green Salad with Yogurt Grapefruit Dressing* Sourdough Rolls Strawberries with Orange Juice, Kirsch or Orange Liqueur *Recipes included

Staples On Hand: Salt, garlic, ground ginger, peanut oil, vinegar, soy sauce, grapefruit juice, Dijon mustard, orange juice and/or liqueur.

Shopping List: Fish fillets, asparagus, Boston lettuce, plain yogurt, sourdough rolls, strawberries. STEAMED ASPARAGUS (2 servings) 16 to 20 thin asparagus spears, depending on how much asparagus you like. Salt to taste

Break off tough ends of asparagus at point where they break naturally. Allow to soak in water for a few minutes to remove any grit.

Bring water to boil in a steamer*. Add asparagus and steam for 8 to 10 minutes, depending on their thickness. When they are crisp tender, remove from heat to stop cooking.

*If you do not have a steamer, you can tie the asparagus into a bundle with some cord and stand them upright in an inch of water in a double boiler. Cover and cook as directed. CHINESE BROILED FISH (2 servings) 3/4 to 1 pound fish fillets, preferably fresh (flounder, blue fish, pollock) 1 small clove garlic 1 teaspoon ground ginger 1 1/2 tablespoons peanut oil 1 tablespoon white vinegar 1 1/2 teaspoons light soy sauce

Crush the garlic in a press and mix with ginger, oil, vinegar and soy sauce.

Place fish fillets on foil in shallow roasting pan. Brush with basting sauce mixture. Allow to sit while preparing rest of meal. Preheat broiler.

To cook, broil fish about 3 minutes, basting twice. Fish is done when flesh flakes easily with fork and is no longer translu- [TEXT OMITTED FROM SOURCE] SALAD WITH YOGURT-GRAPEFRUIT DRESSING (2 servings) 1 head Boston lettuce (any greens will do, but you will need less than a whole head of most 1/2 cup plain yogurt 2 tablespoons grapefruit juice 1 heaping teaspoon Dijon mustard

Wash lettuce. Dry well and break up, dividing between two salad plates. Mix yogurt with grapefruit juice and mustard. Spoon over salad.

Note: If you are serving the rolls, you can heat them up in the oven while the fish is cooking.

If you serve strawberries, wash and stem them after you have finished all the other preparations. Cover them with orange juice or liqueur so they can marinate while you are eating dinner.