Trim crusts from bread slices. Arrange bread slices in bottom of 13 X 9 X 2″ pan or glass dish. Top each bread slice with a slice of process Swiss cheese.
In a bowl, beat eggs slightly; add milk, stir in seasonings and onion. Pour this mixture over sandwiches and bake in slow oven (325°) 25 minutes.
Remove from oven. Top each bread slice with 3 cooked a