Heat oven to 350°.
Sprinkle cavity and outside of goose lightly with salt.
Place onion in cavity.
Add flour to large (or turkey-sized) oven cooking bag.
Shake to distribute.
Place bag in roasting pan.
In a small bowl blend wine, orange juice, lemon juice, and dry mustard.
Add to cooking bag, stir with plastic or wooden spoon to blend into flour.
Place goose in cooking bag, breast side up.
Close cooking bag with provided nylon tie.
Make 6 half inch slits in top of bag.
Roast until almost desired doneness – 15 to 20 minutes per pound.
Slit cooking bag down center and roast until goose is brown, 15 to 20 minutes longer.
Remove goose from bag, discard onion.
Keep goose warm.