Preheat oven to 325°.
Remove and discard giblets and neck from turkey. Trim excess fat. Combine chopped onion, 1/2 teaspoon salt, 1/2 teaspoon pepper, thyme, chopped sage sprigs, marjoram, parsley, and rosemary in a small bowl. Stuff body cavity with onion mixture. Tie legs together with kitchen string. Lift wing tips up and over back; tuck under turkey. Brush turkey with canola oil; sprinkle with the remaining 1/2 teaspoon salt and remaining 1/2 teaspoon pepper. Cover breast with foil. Place turkey, breast side up, on a roasting rack in a roasting pan. Pour 2 cups water into pan.
Bake at 325° for 1 1/2 hours; remove foil, and baste turkey with pan juices. Add 1 cup water to pan, if needed. Bake an additional hour or until a thermometer inserted in the meaty part of the thigh registers 165°, basting every 30 minutes. Remove turkey from oven; let stand at least 30 minutes before carving. Discard onion mixture and skin.
Place a zip-top plastic bag inside a 2-cup glass measure. Pour drippings from pan into bag; let stand 10 minutes (fat will rise to the top). Seal bag; carefully snip off 1 bottom corner. Drain drippings into a bowl, stopping before fat layer reaches opening; discard fat.
Place the roasting pan over two burners on medium heat. Add the turkey drippings, the Make-Ahead Gravy, and 2 teaspoons chopped fresh sage, scraping the pan to loosen browned bits. Reduce heat, and cook until the gravy mixture is reduced to 3 cups, stirring occasionally (about 5 minutes).
Wine note: A wine for your Thanksgiving turkey must be one that will stand up tall to the flavors of the fixings, from the savory meatiness of the gravy to the piquancy of the cranberry sauce to the sweetness of the sweet potatoes and the earthy, richness of the stuffing. A generous, mouth-filling, soft-textured red is a great bet. Here's a terrific one that's powerful but plush: Robert Keenan Merlot from the Napa Valley. The 2003 is $34. -Karen MacNeil