Preheat the oven to 350 degrees. Grease an 8x8 baking dish with cooking spray and set aside. In a large bowl, combine all of the ingredients except the butter. Spread the mixture into the prepared dish and bake for 25 minutes or until the oatmeal is cooked through. Cut the butter into 4 pieces and place on top of the oatmeal and place under the broiler for 2-3 minutes. Let cool for a few minutes before eating.