PREHEAT broiler. Remove and discard stems from mushrooms. Brush mushroom caps with dressing and place on rack of broiler pan. Broil 5 min.
PRESS sausage evenly into mushroom caps, using about 1/2 tsp. sausage in each cap. Sprinkle evenly with cheese.
BROIL an additional 5 min. or until cheese is melted. Serve hot.