Heat oven to 400°F.
Combine ground beef, bell pepper and onion in 12-inch skillet. Cook over medium-high heat, stirring occasionally, 6-8 minutes or until onion is softened and beef is browned.
Drain off fat. Stir in mushrooms, pasta sauce and olives.
Spoon mixture into ungreased 13×9-inch baking pan. Top with cheese slices. Place into oven while preparing topping.
Beat eggs in bowl at medium speed, scraping bowl often, until light and lemon-colored.
Add milk and melted butter; continue beating 1 minute.
Stir in flour and salt, with wire whisk, until smooth.
Pour mixture over hot filling, spreading to cover filling completely. Sprinkle with Parmesan cheese.
Bake 25-30 minutes or until top is puffed and golden brown. Serve immediately.