Preheat your oven to 350°F (175°C).
In a large pot, heat the olive oil over medium heat. Add the diced chicken and season with salt, pepper, garlic powder, and onion powder. Cook until the chicken is no longer pink, about 5-7 minutes.
Stir in the broccoli florets and cook for an additional 2-3 minutes until slightly tender.
In a mixing bowl, combine the cream of chicken soup, milk, and half of the cheddar cheese. Mix well to create a creamy sauce.
In a large baking dish, combine the cooked rice, chicken and broccoli mixture, and cheese sauce. Stir until everything is evenly distributed.
Top the casserole with the remaining cheddar cheese and, if desired, sprinkle breadcrumbs on top for a crunchy finish.
Bake in the preheated oven for 30 minutes, or until the casserole is bubbly and the cheese is melted and slightly golden.
Remove from the oven and let it rest for a few minutes before serving.