To avoid risks of sickening your family with salmonella and other poultry-born bacteria, prepare and cook a turkey according to its weight. The more pounds, the longer it takes to cook. Give yourself enough time when cooking a 30-lb. turkey.
Defrost the turkey in the refrigerator or in a water bath in the sink. The latter takes less time but increases the risk of bacteria developing. For refrigerator defrosting, allow 24 hours for every 5 lbs. of turkey. A 30-lb. turkey should thaw in the refrigerator six to seven days. For the sink water bath method, begin the thawing the night before. Let it rest in the water for at least 15 hours.
Before cooking time begins, preheat the oven and dress the bird. This should take about a half hour. Preheat the oven to 325 degrees Fahrenheit and rinse the thawed turkey in water, cleaning away all excess innards and skin. Tie the legs of the turkey together with twine and massage butter into and under the skin. Sprinkle with salt, pepper, and turkey seasonings, including thyme, parsley and poultry seasoning. Place turkey in a pan and fill with 2 cups of chicken stock and chopped vegetables, such as onions, garlic and celery.
The roasting time for a 30-lb. turkey is between 5-1/2 and 6-1/4 hours. During the roasting, periodically check the moisture and baste. Replenish the stock or water if evaporated. Use a meat thermometer to check the doneness of the turkey, even if the timetable is followed. The inside temperature of the thigh should be 180 degrees and 170 degrees in the breast. If using stuffing, the core of the stuffing must reach 180 degrees.