Tie wings to body, tuck in or tie legs together securely with string.
Season the inside of the turkey with salt and pepper.
Stuff the turkey cavity with onion, celery, lemon, and fresh herbs.
Place turkey breast side up in a large (BBQ-safe) roasting pan.
Rub turkey with olive oil or butter and season with salt and pepper.
Add ½ cup water to the bottom of the pan.
Place pan on grills preheated to medium and close lid.
After 20-30 minutes, lower heat to medium-low and tent turkey with foil to prevent over-browning.
Baste turkey with drippings every 15-20 minutes.
For barbecues with temperature settings, keep barbecue adjusted to 160-190ºC (325-375ºF).
Add more water to pan if it dries out during cooking.
3.5-4.5 kg (8-10 lbs): 1-2 hours
4.5-5.5 kg (10-12 lbs): 1½ - 2½ hours
5.5-7.0 kg (12-16 lbs): 2 - 2½ hours
Remove the bird from pan and transfer to a cutting board.
Tent with foil and let stand for 10 minutes before carving.
Don't forget the cranberry sauce!