Cook bacon, crisp. Remove from pan and crumble.
Cook onion in some of the bacon drippings until soft.
Spread half the bread in a 9x13 dish. Sprinkle with half the bacon, half the onion and half the cheese. Repeat layers.
Combine eggs, milk, salt and pepper. Pour egg mixture over the top layer in dish. Chill overnight.
Bake at 325° for about 1 hour until set and puffed.
**NOTE: For 4 to 5 servings, reduce by half and bake in 8 inch square pan.