Oven Bag Roasted Turkey

12 pounds whole turkey
salt and pepper to taste
2 tablespoons all-purpose flour
5 stalks celery
2 large onions, quartered

Directions::

Preheat oven to 350 degrees F (175 degrees C). Rinse turkey and remove giblets. Salt and pepper to taste.
Sprinkle the bottom of a turkey size oven bag with flour. Place turkey, celery and onions in the bag. Seal bag and poke several holes in it with a fork. Bake 3 to 3 1/2 hours, or until internal temperature of the thigh meat reaches 180 degrees F (85 degrees C).