Preheat the oven to 400 degrees. In a casserole dish smear the butter all over the bottom of it. Place the 4 chicken breasts into the dish and place in oven for 20 minutes.
Flip the chicken over and bake in oven for 20 minutes.
Flip the chicken over and pour the whole bottle of bar-b-que sauce over the chicken. Bake for 20 minutes. Serve chicken and you can use the extra butter/sauce that the chicken is swimming in to pour over your chicken or to dip into.