I did an 11 lb. turkey with stuffing on the BBQ for Christmas (so I wasn't an adult when Canada went metric -- why do we still buy our meat in pounds?). I took the temperature of the stuffing at three hours and it was ready (165 F -- again, still cooking in Imperial units). It was nice and moist so I don't think it had been ready for long.
The BBQ is great for a couple of reasons: The rotisserie keeps the juices in the turkey, not in the dripping pan. Also, gas heat is moister than the electric heat that many of us have in the oven in the kitchen.
11 lbs. is the maximum-sized turkey I could do in my BBQ, which is a fairly standard domestic gas BBQ. That's okay, as it's still way too big for our family.