Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the rice, cream of chicken, cream of mushroom, cream of celery, water (or broth), garlic powder, onion powder, salt, and pepper. Mix until smooth.
Pour the mixture into a greased 9x13-inch baking dish.
Lay the chicken breasts evenly over the rice mixture.
Sprinkle the onion soup mix evenly over the top.
Cover the dish tightly with aluminum foil—do not peek!
Bake for 1 hour and 30 minutes, then remove from the oven.
Let rest for 5–10 minutes before serving.