We started cooking our turkey on the grille many, many years ago. Reason being it was warm, we all lived in Southern California and nothing worse than heating up the kitchen when it's 80+ degrees.
OK on to the method..............
When we are all together, there aren't very many of us. So a 10 - 15 pound turkeyfor us was way plenty.
1. fire up the grille to good and hot 425 at least.
2. the bird should be sitting on the counter, ya don't want it iced cold when you put him on the grille. Follow your package directions for cleaning said bird please. I rub the turkey with butter on the outside and put celery and carrots on the inside after salting inside.
3. the bird should be in a proper size oven proof pan. I like to line the pan with foil cause it's a bit less clean up. Make sure the lid of your grille is able to close and there is enough circulation around to cook.
4. A 15 pound unstuffed turkey cooks on a grille for about 3 3 1/2 hours with an internal temperature using an instant meat thermometer should be 165 - 175 degrees. Your grille should be between 325 and 350, don't let it go over 350 cause it will guickly dry our and not brown.
Go to the Butterball web site for ideas. Hope I didn't forget anything.
Happy Turkey Day