Preheat the pellet smoker to high. Place a cast iron skillet over the highest heat spot and cook the bacon until crisp.
Remove the bacon from pan and drain, reserving the bacon fat in the pan.
Reduce the heat on your smoker to 250°F.
Add the onions, garlic, and brussels to the pan and toss to coat in the bacon drippings. Sprinkle the BBQspice blend over top.
Cover the lid and allow to smoke for 1 to 1 1/2 hours, until the sprouts are fork tender.
For the last 20 minutes of smoking, toss the brussels sprouts in half of the barbecue sauce.
Remove the sprouts from the smoker.
Chop the bacon and add it and the remaining barbecue sauce to the pan of sprouts, tossing to coat.