I found this on allrecipes.com.
1 (32 oz) package frozen hash brown potatoes
8 ounces cooked, diced ham
2 (10.75 oz) cans condensed cream of potato soup
16 oz sour cream
2 cups shredded sharp cheddar
1 1/2 cups grated parmesan cheese
Preheat oven to 375 degrees. Lightly grease 9x13 baking dish.
In a large bowl, mix the hash browns, ham, soup, sour cream, and cheddar. Spread evenly into the baking dish and sprinkle with parmesan.
Bake for one hour or until bubbly and light brown.