Arrange the eggplant slices on a baking sheet coated with cooking spray; broil 3 minutes on each side or until lightly browned.
Preheat oven to 375°.
Heat a large nonstick skillet coated with cooking spray over medium heat; add onion and next 4 ingredients (onion through mushrooms). Cover and cook 7 minutes or until tender, stirring mixture occasionally. Increase heat to medium-high; uncover and cook for 2 minutes or until liquid evaporates.
Spread half of mushroom mixture in bottom of a 1 1/2-quart round baking dish coated with cooking spray. Arrange half of eggplant slices over mushroom mixture; sprinkle with 1/8 teaspoon pepper. Top with 1/2 cup tomato sauce and 1/3 cup mozzarella. Spread remaining mushroom mixture over mozzarella; top with remaining eggplant slices. Sprinkle with 1/8 teaspoon pepper; top with remaining tomato sauce. Cover and bake at 375° for 1 hour. Sprinkle with 1/3 cup mozzarella and Parmesan. Bake, uncovered, 5 minutes or until cheese melts. Let stand 10 minutes.