Cooking a 20-pound turkey requires careful planning and execution to ensure it is cooked evenly and safely. The general rule is to cook the turkey at 325F (163C) for 4-5 hours, or until the internal temperature reaches 165F (74C) as measured by a meat thermometer inserted into the thickest part of the thigh without touching bone.
It is important to note that cooking times may vary depending on the size and shape of the turkey, as well as the accuracy of your oven. To ensure the turkey is cooked through, it is always best to use a meat thermometer. Once the turkey has reached the desired internal temperature, let it rest for 30 minutes before carving to allow the juices to redistribute, resulting in a more flavorful and tender bird.