Place cleaned chicken breasts in a 9 x 13 inch glass baking dish or casserole dish. Arrange the sliced onion pieces evenly on top of the chicken pieces. Scoop the mushroom soup onto the chicken and onions. Mix the peppercorn gravy with water and pour it
over the soup, onions and chicken.
Cover the dish and bake for 1 hour, stirring the chicken and mixture after 30 minutes. If desired, serve over rice or with mashed potatoes.