PLACE vegetables and tomatoes in large bowl. Add dressing; toss to coat. Let stand 20 min. to marinate, stirring occasionally. Remove vegetable mixture from marinade; reserve marinade for later use.
PREHEAT barbecue to medium heat. Place vegetable and tomato pieces on grate of barbecue. Grill 8 min. or until vegetables crisp-tender, turning occasionally.
PLACE vegetable mixture in large bowl. Add the reserved marinade; toss lightly.