Thaw broccoli and warm in the microwave for about 5 minutes.
Drain very well.
In a bowl combine the cooked rice, onion, cream of mushroom soup, milk, salt & pepper, garlic powder, and 1 cup of the shredded cheese together until well mixed.
Spoon into a greased 9 x 13-inch baking dish.
Top with the remaining 1 cup of shredded cheddar cheese.
Bake in a pre-heated 350° oven for 35-40 minutes or until bubbly.