You can make this the night before and bake just before you need it.

1 24-ounce package frozen O'Brien hash brown potatoes
3/4 cup shredded cheddar cheese, divided
1 can Campbells cheddar cheese soup
1 can Campbells cream of celery soup
2 cups cubed fully cooked ham
1 small onion, chopped
2 cups sour cream
1/4 teaspoon pepper

In a large bowl, combine potatoes, ham, 1/2 cup shredded cheese and onion. In another bowl, combine sour cream, soups and pepper; add to potato mixture and mix well. Transfer to a greased 3 quart baking dish. Sprinkle with remaining shredded cheese. Can be made up to here the night before. Bake, uncovered at 350 degrees for 60 minutes or until bubbly and potatoes are tender. Let stand for 10 minutes before serving.