Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, add the olive oil. Once hot, add the chicken thighs and cook until browned on both sides (about 4-5 minutes per side). Remove from heat and set aside.
In a mixing bowl, combine the cream of mushroom soup, cream of chicken soup, chicken broth, onion soup mix, garlic powder, and black pepper. Stir until well mixed.
In the greased 9x13 inch baking dish, spread the uncooked rice evenly on the bottom.
Pour the soup mixture over the rice, spreading it evenly.
Place the browned chicken thighs on top of the soup mixture. Then, scatter the sliced mushrooms over the chicken.
Cover the baking dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 15 minutes, or until the chicken is cooked through and the rice is tender.
Once done, remove from the oven and let it sit for 5 minutes before serving.
Garnish with fresh parsley if desired.