This crustless four-cheese quiche is a delicious and easy-to-make dish that is perfect for breakfast, brunch, or even dinner. It is packed with four different types of cheese - cheddar, mozzarella, Swiss, and Parmesan - which gives it a rich and creamy flavor. The quiche is also loaded with sautéed vegetables like onions, bell peppers, and spinach, adding a burst of freshness and color. Serve it warm or at room temperature for a satisfying and comforting meal.