Velma Phillip’s Cheesy Potatoes

1 package frozen hash brown potatoes (32 oz.), thawed

1 medium sized onion diced

2 cups sour cream

1 can cream of mushroom soup

2 cups shredded cheddar cheese

1 stick butter, melted

Mix all together in a large bowl, then put in 9x13 casserole.  Bake one hour at 350 degrees.