1. Prep the oven to heat to 350F, and meanwhile, liberally season the chicken in a roasting pan with pepper and salt. Ensure to rub the seasoning inside the cavity as well.
2. Sprinkle onion powder on the surface and inside the cavity, followed by half of the margarine. Dollop the remaining half around the bird’s exterior, and add celery sticks into the cavity.
3. Cook the chicken uncovered at 20 minutes per pound, which will take up to an hour, plus 15 minutes for the celery sticks. Check the internal doneness with a meat thermometer by sticking it to the thickest region of the inner thigh. The chicken is ready when the temperature hits 165F.
4. Take the bird out and baste with the pan drippings for a few moments, then tent it with foil for 30 minutes before carving.

You can also follow this video recipe for more help.