Combine mushrooms, cauliflower, broccoli, carrots & onion in a large bowl; sprinkle with basil, salt & pepper. Divide vegetable mixture evenly onto 4 (18 inch) squares of foil. Dot each with 1 ts Margarine. Using the pyramid wrap method, bring the four corners of foil together in a triangle shape; fold open edges together in loosely locked folds, allowing for heat circulation & expansion. Repeat procedure for other packets. Grill vegetables 5 to 6 inches from medium coals 8 min. Or until crisp-tender.