Preheat oven to 350ºF.
In a greased medium skillet, add ground beef, onions, garlic powder, salt, and pepper.
Cook until beef is cooked through and onions are transparent.
In a large mixing bowl, combine hash browns, vegetables, and 1 cup shredded cheese. Stir well.
Add ground beef mixture, cream of chicken, and cream of mushroom. Stir well.
Transfer mixture to a greased 9-13-inch baking dish.
Top with remaining 1 cup of shredded cheese.
Cover with aluminum foil and bake for 30 minutes.
Remove foil and bake for an additional 5 minutes or until cheese is completely melted and bubbly.