HEAT oil in large skillet on medium heat. Add vegetables; cook and stir 5 min. or until crisp-tender. Add Mastering the Meatlball and barbecue sauce; mix lightly. Cook 3 min. or until heated through, stirring occasionally.
HEAT broiler. Spoon 4 meatballs into each bun; top with vegetable mixture and cheese. Place on rack of broiler pan.
BROIL, 6 inches from heat, 2 min. or until cheese is melted.
serving size = 1 sandwich (300 g)