Layer in casserole:

2 c. frozen hash browns, thawed
1 c. Cheddar cheese, shredded
2 tbsp. onion, chopped
1/2 to 1 lb. browned sausage
1 (4 oz.) can mushrooms, sliced and drained

Mix, then pour over layered ingredients:

4 eggs, beaten
1/2 tsp. salt
1/2 tsp. pepper
3 tbsp. milk

Bake at 350 degrees for 45 minutes.