Heat gas or charcoal grill. In large bowl, combine zucchini, summer squash, salad dressing and pepper flakes; toss to coat. Place zucchini and squash in grill basket (grill "wok"). Reserve mixture in bowl.
When grill is heated, place grill basket on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 10 to 12 minutes or until vegetables are tender, stirring occasionally.
Add tomatoes to mixture in bowl; toss to coat. Add warm zucchini and squash; toss to coat. Sprinkle with cheese. Serve with slotted spoon.