I've done a cabbage as follows, I don't know if this is the same method though.
crumple tinfoil to make aring to support the cabbage
core the cabbage and place in the ring with hollowed out core up
cook several slices of bacon
fill core with chopped onionand garlic and the bacon and bbq sauce top with several pats of butter
I can't remember how long I smoked it for sure I think that it was about 2 hours
Ithink I originally found the recipe in one of Raichlen's books