Brunch Baked Omelet (3 pans for 40 people)

This recipe is for one pan.
 

1 box seasoned croutons
3 cups cubed ham or turkey
4 cups shredded Cheddar cheese
6 eggs
3 cups milk
2 tsp dry mustard
Salt and pepper

Arrange croutons, cheese and ham in buttered 9" x 13" pan. In separate bowl beat eggs, dry mustard, salt, pepper and milk. Pour slowly into pan. Bake at 350 one hour. Eggs will start to pull away from edges of dish when ready. Let set 5 minutes or so, cut into squares.