In a large mixing bowl, combine both cans of cream of chicken and mushroom soup with chicken broth, garlic powder, onion powder, thyme, salt, and pepper, stirring well until smooth.
In a greased 9x13 inch casserole dish, spread the uncooked rice evenly along the bottom.
Pour the soup mixture over the rice, gently spreading it to cover all the rice.
Place the chicken breasts on top of the liquid mixture, seasoning them with a little more salt, pepper, and thyme for extra flavor.
Sprinkle the frozen mixed vegetables around the chicken breasts in the casserole dish.
Cover the dish tightly with aluminum foil, making sure it's sealed well to keep the moisture in.
Bake in the preheated oven for 1 hour.
After 1 hour, carefully remove the foil and sprinkle the shredded cheddar cheese over the casserole.
Return to the oven, uncovered, for an additional 15-20 minutes, or until the cheese is melted and bubbly, and the chicken is cooked through.
Remove from the oven and let it sit for 10 minutes before serving to allow it to set.
Notes
Let the casserole sit for 10 minutes before serving to allow it to set.