Breakfast Casserole

Found this Breakfast Casserole recipe online.
Christmas morning-perfect!

1 (30 oz) package frozen shredded hash brown potatoes, thawed
1 onion, diced
1 lb ground sausage, browned and drained
2 cups shredded strong cheese (sharp cheddar, swiss, etc)
1 green pepper, slice a couple of rings for garnish, dice the rest
1 red pepper, slice 6-7 rings, dice the rest
1 c. sliced mushrooms
12 eggs
2 cups milk
1/2 t. salt
1/4 t. ground black pepper

Drain potatoes, and fry in frypan with onion to get most of the moisture out.  Assemble remaining ingredients, pouring the egg/milk mixture over the top.  Garnish the top with pepper slices.
Bake in a 325-degree oven for 1 hour, or until inserted knife comes out clean, and eggs are set.

Top with green onions, salsa, tomatoes, mushrooms, avocado, etc.