Preheat oven to 350 degrees F (175 degrees C).
In a large bowl mix the rice, dry onion soup mix, cream of mushroom soup, mushroom pieces and milk.
Place the chicken pieces in a 9x13 inch baking dish and pour the mushroom mixture over the chicken. Cover and bake in the preheated oven for 1 hour. Uncover and bake for 15 more minutes.