A rule of thumb to determine turkey size required is to allow 1 lb (500 g) uncooked weight per serving, plus leftovers.
Preheat oven to 180ºC (350ºF). Position rack in lower third of oven. To make stuffing, melt butter in skillet over medium heat. Cook celery, onion, and sage 3 to 5 min. until softened. Cool completely. In large bowl, combine bread, onion mixture, salt and pepper. Stir in just enough broth to thoroughly moisten bread without sogginess.
Remove turkey giblets and neck, if there are any, from turkey cavity and place in roasting pan. Pat turkey dry with paper towel. Rub oil, salt and pepper on skin and inside cavity. Immediately prior to roasting, loosely fill turkey cavity with stuffing. Tie legs together with butcher’s twine. Tuck in wing tips. Also, put some stuffing in the neck cavity (there will be leftover stuffing). Pull over neck skin and use skewers to close up cavity.
Place turkey, breast-side up, in roasting pan fitted with rack. Place leftover stuffing in a covered baking dish or foil packet (a packet is easier to fit into a full oven); set aside.
To determine turkey’s roast time, allow 20 min. for every 1 lb (500 g). To check doneness for sizes up to 12 lb (5.5 kg), check internal temperatures regularly during last 45 min. of roasting. For larger turkeys, check regularly during last 1 ½ hr. Baste periodically with pan drippings for browner skin, if desired. The thickest part of inner thigh should register 85°C (185°F) and stuffing should reach 74°C (165°F).
Untie legs. Immediately remove stuffing from turkey; set aside. Transfer turkey to serving platter. Tent loosely with foil; let rest 30 min. Reserve pan drippings for gravy. While turkey is resting, place baking dish (or packet) of stuffing into oven. Bake about 30 min., or until hot.
Meanwhile, use pan drippings to make Herbed Turkey Gravy. When the baking-dish stuffing is ready, mix it with the stuffing from the turkey; transfer into a serving bowl. Carve turkey, serve with stuffing and gravy.
Whole-wheat or challah bread are also delicious used in stuffing.
Mixing the wetter stuffing from the turkey with drier stuffing in baking dish results in best texture and flavour.
Bake all the stuffing in large covered, baking dish and roast turkey unstuffed.