HEAT grill to medium-high heat.
GRILL corn 15 min. or until kernels are browned and tender, turning occasionally; cool slightly. Meanwhile, grill squash and zucchini 5 min. or until tender, turning occasionally.
CUT kernels off cobs; place in medium bowl. Chop squash and zucchini. Add to corn with tomatoes; mix lightly.
MIX dressing, lemon juice and garlic. Add to vegetable mixture; mix lightly. Top with Parmesan and basil.