Gather your cooked chicken, shred or dice it into bite-sized pieces. Wash and chop broccoli into small florets.
If using raw chicken, cook it in a skillet with olive oil over medium heat until golden brown, about 6-8.
Sauté sliced mushrooms in the same skillet for about 5 until tender and slightly browned.
In a large bowl, combine cream of mushroom soup, milk, garlic powder, onion powder, salt, and pepper. Whisk until smooth.
Add cooked chicken, cooked rice, broccoli florets, and sautéed mushrooms to the creamy sauce. Stir gently to coat.
Preheat oven to 350°F. Pour mixture into a greased 9x13-inch baking dish, sprinkle cheese on top, cover with foil, and bake for 25. Remove foil and bake for an additional 10-15 until cheese is bubbly and golden brown.
Let cool for a few minutes before serving.