Place the turkey breast skin side up in a roasting pan. Preheat the oven to 325 degrees. Add 1/4 cup of water to the bottom of the pan and cover the breast with foil.Cook a 4-pound breast for 1 1/2 hours and an 8-pound breast for 3 hours, 15 minutes.For turkey breasts in between those sizes, allow approximately 25 minutes per pound. The breast is cooked when the internal temperature reaches 165 degrees.reheat your oven to 325 degrees. Unwrap the turkey and remove the giblet package and neck bone from the inner cavity. Rinse the bird with running cold water and place it in your roasting pan. Add approximately 1/2 cup of water to the pan to help keep the turkey skin from sticking to the pan.