COOK first 5 ingredients in large ovenproof skillet on medium heat 5 min. or until crisp-tender, stirring frequently.
STIR in tomatoes; cook 15 min., stirring occasionally. Top with cheeses.
HEAT oven to 350ºF. Bake vegetable mixture 15 min. or until golden brown.
serving size = 1 cup (250 mL)