A 15 pound turkey feeds about 10 people with a bit leftover for casserole. A 15 pound turkey will hold about 7 cups of stuffing
Thaw your turkey in the fridge for about 5 hours per pound or in cold water for about 1 hour per pound (make sure to change your water a few times). If you do nothing else right, make sure you get the darn thing defrosted in time!! I'm speaking from experience *blush*.
To prepare your turkey, remove giblets and neck. Rinse turkey inside and out. Dry skin and cavity well. Fill neck and body with stuffing and pin closed with a skewer (if you have one.
If you're the stove top stuffing type, cut some onions and garlic in half, sprinkle with salt, pepper and thyme (or use fresh thyme sprigs) and stuff the turkey with that just to add a bit of flavour (and make yourself feel like you've actually put some effort into the bird).
Place on a rack in a roaster and rub with butter (¼ to ' cup). Sprinkle on poultry seasoning or thyme and salt and pepper.
Cover with roaster lid (if it's big enough) or make a aluminum foil lid. Roast in a preheated 325 degree F oven for about 4 hours. Baste every ' hour or so if you're the basting type.
Remove the lid (foil) and roast for another hour or until it's a nice color. A meat thermometer in the thigh should read about 185 degrees F.
Let it stand on a platter for about 15 minutes before you carve.