Preheat oven to 350 degrees F (175 degrees C). Rinse turkey, remove giblets and place in a shallow roasting pan.
Prepare stuffing according to package directions. Mix in water.
Melt butter in a medium saucepan over medium heat, and slowly cook and stir the celery and onion until tender.
Mix celery, onion, and toasted bread pieces into the stuffing, and season with salt and pepper. Loosely scoop stuffing into the turkey body cavity and neck cavity. Rub the exterior of the turkey with vegetable oil.
Loosely cover turkey with aluminum foil, and roast 3 1/2 to 4 hours in the preheated oven, until the thickest part of the thigh reaches 180 degrees F (85 degrees C) and the interior of the stuffing reaches 165 degrees F (70 degrees C). Remove foil during the last half hour of cooking to brown the bird.