HEAT greased grill to medium heat.
COMBINE first 4 ingredients.
USE spoon to remove stems and brown gills from undersides of mushroom caps; discard. Mix dressing and garlic; brush onto both sides of mushroom caps.
GRILL, top-sides up, 5 min.; turn. Top with vegetable mixture; grill 5 min. or until mushrooms are tender and cheese is melted. Sprinkle with basil.