Preheat the oven to 350°F and lightly grease a 9x9 inch baking dish.
In a large mixing bowl, combine the cooked rice, shredded chicken, cream of chicken soup, milk, 1 cup of the cheddar cheese, garlic powder, salt, and black pepper. Stir until everything is evenly mixed.
Spread the mixture into the prepared baking dish and smooth the top.
Sprinkle the remaining 1 cup of cheddar cheese evenly over the surface.
Bake for 25 to 30 minutes, until the cheese is melted and bubbly and the edges are lightly golden.
Remove from the oven and let it rest for 5 minutes before serving.