Preheat oven to 450°F. Place hash brown patties in single layer in 13x9-inch baking dish sprayed with no stick cooking spray. Bake 20 minutes or until browned, turning after 10 minutes. Remove from oven. Let stand 5 minutes. Reduce oven temperature to 350°F.
Beat eggs in large bowl with wire whisk. Add milk, sour cream, garlic powder, mustard and pepper; mix well. Stir in bacon, 1 1/2 cups of the cheese and onions. Pour over hash brown patties. Sprinkle with remaining 1/2 cup cheese.
Bake 40 to 50 minutes or until center is set and edges are golden brown.