1.Preheat oven to 350°F. Coat 13x9 baking dish with nonstick cooking spray.
2.In a large bowl, whisk together soup, sour cream, salt and pepper. Stir in cheese, onion and hash browns until well mixed. Spoon evenly into baking dish.
3.In a medium bowl, mix together cereal and butter. Sprinkle evenly on top of hash brown mixture.
4.Bake uncovered for 45 to 50 minutes, or until hot and bubbly. Allow to rest for 5 minutes before serving. Season with additional salt and pepper to taste if desired. Garnish with additional sliced green onion if desired.