Heat oven to 325°F. Grease 13x9-inch (3-quart) glass baking dish with shortening or cooking spray; set aside. Remove and discard neck and giblets from turkey. Rinse turkey inside and out with cold water; pat dry with paper towels. In small bowl, mix sage, salt and pepper; rub into turkey skin.
In 8-inch skillet, melt butter over medium heat. Add onion; cook 4 to 6 minutes, stirring occasionally, until tender. In large bowl, thoroughly mix cooked onion and remaining stuffing ingredients.
Turn turkey breast side down. Fill neck cavity lightly with 1 cup of the stuffing (do not pack stuffing because it will expand during roasting). Fasten neck skin of turkey to back with skewer.
Turn turkey breast side up. Fold wings across back of turkey so tips are touching. Fill body cavity lightly with 3 cups of the stuffing (do not pack stuffing because it will expand during roasting). Place remaining stuffing in baking dish. Cover with foil; refrigerate until ready to bake. Tuck legs under band of skin at tail (if present), or tie together with heavy string.
On rack in shallow roasting pan, place turkey, breast side up. Insert ovenproof meat thermometer so tip is in thickest part of inside thigh and does not touch bone.
Cover turkey loosely with foil or roaster cover; roast 3 hours. Meanwhile, in small bowl, mix glaze ingredients; set aside.
Uncover turkey and place foil-covered baking dish with stuffing in oven. Roast 45 minutes to 1 hour 30 minutes longer, brushing turkey with glaze frequently, until thermometer reads 165°F and drumsticks move easily when lifted or twisted. Thermometer inserted in center of stuffing in turkey should read 165°F. Remove baking dish with stuffing from oven after 40 to 50 minutes of baking time or when thoroughly heated (165°F).
Place turkey on warm platter; cover with foil to keep warm. Let stand about 15 minutes for easiest carving. Cover and refrigerate any remaining turkey and stuffing separately.