My mom has made this many times for holidays or company and when I needed a potato dish for a friend after she had her baby, I immediately thought of this cheesy casserole.  Happy eating!
Cheesy Hash Brown Casserole Ingredients:

1-32 oz. frozen hash brown potatoes (thawed)
Small onion, chopped
1 can cream of mushroom or chicken soup
1/2 cup sour cream
1/2 cup melted butter
2 cups grated cheddar or Colby jack cheese
Salt and pepper to taste

 Instructions:

Mix all of the ingredients and put in a pan sprayed with cooking spray.  Bake at 350* for 45 minutes or until bubbly.
(I added some extra cheese on top for the last 5 minutes in the oven)