Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, broccoli, rice, chicken broth, cream of mushroom soup, garlic powder, salt, and pepper.
Add half of the shredded cheddar cheese to the mixture and stir until well combined.
Transfer the mixture to a greased 9x13 inch baking dish.
Top the casserole with the remaining cheddar cheese.
Cover the dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Let the casserole cool for about 5-10 minutes before serving.