Cook the rice according to the package directions and set it aside.
Steam the broccoli florets for 4 minutes until they turn bright green and still feel firm.
Melt the butter in a skillet over medium heat and cook the diced onion until it softens.
Stir in the cream of chicken soup, milk, garlic powder, salt, and pepper until the mixture is smooth.
Combine the cooked rice, steamed broccoli, and half of the shredded cheddar cheese in a large bowl.
Pour the soup mixture over the rice and broccoli and stir until everything is evenly coated.
Transfer the mixture to a greased baking dish and sprinkle the remaining cheese on top.
Bake at 350°F for 20 minutes until the cheese is melted and the edges start to bubble.