1Heat oven to 350.
Melt butter in medium skillet over medium heat. Add chopped onion. Saute until tender. Whisk in flour until thouroughly combined. Add milk, continue stirring until thick. Add cheeses, stir until melted.
Place 1/2 of the egss in bottom of 8x8 baking dish. Pour 1/2 the cheese sauce over the eggs. Sprinkle with 1/2 the bacon and 1/2 f the fried onions. Repeat layers. Bake uncovered 15 to 20 mins or until heated through.