In 12-inch nonstick skillet, melt remaining 2 tablespoons butter over medium heat. Cook onion, bell pepper and mushrooms in butter 3 to 5 minutes, stirring occasionally, until vegetables are crisp-tender. Add beaten eggs. Cook, stirring occasionally, until eggs are set; remove from heat. Gently stir in bacon and Alfredo sauce. Spread in baking dish. Sprinkle with topping.