Preheat oven to 350°F (190°C) and grease a 9x13-inch baking dish or casserole dish.
In a large bowl, combine cooked brown rice, chicken, broccoli, 1 cup shredded cheese, cream of chicken soup, milk, garlic powder, onion powder, salt, and pepper. Mix until well combined.
Spread the mixture evenly into the prepared baking dish or bowl.
Top with additional shredded cheese and breadcrumbs, if desired.
Bake for 15 minutes covered. Then remove cover and cook another 10, or until the casserole is bubbly and the cheese is melted and golden.