HEAT oven to 400°F. Mix stuffing mix and hot water; set aside. Remove stems from mushrooms; chop stems. Melt margarine in skillet. Add stems and garlic; cook and stir until tender. Add stuffing with spinach and cheeses; mix well.

SPOON into mushroom caps. Place, in shallow baking pan.

BAKE 20 min. or until mushrooms are tender and filling is heated through.