Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, steamed broccoli, cooked rice, and cream of chicken soup.
Add in the milk, cheddar cheese, garlic powder, onion powder, and season with salt and pepper. Stir until well mixed.
Transfer the mixture to a greased 9x13-inch baking dish, spreading it evenly.
If using breadcrumbs, sprinkle them evenly over the top of the casserole.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and continue baking for an additional 15-20 minutes, or until the top is golden and bubbly.
Let the casserole cool for a few minutes before serving.