Cooking a turkey requires a bit of forethought, especially if you have bought a frozen turkey. According to the Food Safety and Inspection Service of the USDA, it can take up to six days to thaw a 20-pound turkey in the refrigerator. The amount of time it takes a turkey to cook depends on your oven temperature and whether the turkey is stuffed or unstuffed while cooking.
Cooking an Unstuffed Turkey
Preheat 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. Cover the bird with the roaster lid or foil and cook for at least 4 hours for a 20-lb. turkey. Remove the lid and allow the turkey to cook and brown for another hour. Use a meat thermometer in the thickest part of the breast and thigh to determine doneness. A turkey is fully cooked when the internal temperature is 165 degrees. Allow the turkey to rest for at least 20 minutes after removing it from the oven before you carve it.
Cooking a Stuffed Turkey
A stuffed turkey is cooked the same way as an unstuffed bird, but it needs to be roasted longer. You should stuff the dressing into the turkey cavities immediately before putting the bird into the preheated oven. Test for doneness after 5 hours for a 20-lb. turkey by using a meat thermometer in the breast, thigh and the stuffing and getting a reading of at least 165 degrees in all three areas.
Roasting a Turkey Breast
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.
Roasting a Pre-Stuffed Frozen Turkey or Breast
Frozen stuffed turkeys and stuffed turkey breasts should be cooked according to the instructions on the package. Most frozen pre-stuffed turkeys are cooked from the frozen state and should not be thawed before roasting.