Prepare a grill or preheat the broiler. Grill or broil bell peppers, skin-side towards the flame, until the skin is blackened, 5 to 10 minutes. Place in a paper bag and set aside for 15 minutes. Meanwhile, brush zucchini and onion slices with oil and grill or broil until well browned and tender, about 5 minutes. Chop coarsely and set aside. Peel the peppers. Coarsely chop the yellow pepper and set aside with the reserved zucchini and onions. Place the red peppers in a food processor or blender, along with tomatoes, garlic and oregano; puree until smooth.Transfer to a bowl and stir in 1 cup waer, basil, vinegar and the reserved chopped vegetables. Season with salt and pepper. Cover and refrigerate until cool, about 30 minutes. The soup can be stored covered in the refrigerator for up to 2 days. Per serving: 56 cal; 2 g protein; 1 g fat; 11 g carb; 12 mg sod; 0 mg chol Eating Well, July/August 1993/MM by DEEANNE