1. Preheat oven to 400° F.
2. Grease an 10 1/2" au gratin dish or a large deep pie dish.
3. In a large bowl, using a wire whisk, beat eggs.
4. Add milk, onion, butter, salt and pepper and beat again until well blended.
5. Into the greased dish, pour the mixture and sprinkle cheese and bacon evenly over top.
6. Place the dish in oven and bake for 20 minutes until set and golden brown.
7. Serve with sausage and scalloped potatoes for brunch or with a salad for lunch.