HEAT oven to 400°F.
LAYER half each of the eggplant and mushrooms in 13x9-inch pan sprayed with cooking spray; top with layers of 1/3 each of the Parmesan and mozzarella. Repeat layers.
TOP with spaghetti sauce; cover.
BAKE 35 min. Remove foil. Sprinkle casserole with remaining cheeses. Bake, uncovered, 5 min. or until mozzarella is melted.