Easter Egg Brunch Casserole

This is a wonderful dish for an Easter Sunday brunch or buffet.

18 eggs
1 cup sour cream
1 cup milk
1/4 cup onion, diced finely
1/4 cup cooked bacon (optional)
1/2 to 3/4 cup grated Swiss and Cheddar cheese
1/4 pound butter (not margarine)

In a 9 x 13-inch pan, heat butter to melt in the oven. Beat the eggs, then add the milk and sour cream to blend. Add onion, bacon and cheese; stir. Bake at 350 degrees F for 35 minutes. It is done when a knife inserted in the center comes out clean.