When ready to cook, start your Traeger on Smoke with the lid open until the fire is established (4 to 5 minutes). Set temperature to 225F and pre-heat, lid closed (10-15 minutes).
Begin by cutting off the tops and bottoms of the onions and ridding them of the tough exterior skin. Slice your onion in half and start to peel the layers of the onion apart; set the onion shells aside.
In a large bowl add ground beef, diced onion, parsley, mushroom, diced onion, ketchup, soy sauce, Worcestershire Sauce, brown sugar, Traeger Prime Rib rub, and bread crumbs. Mix by hand.
Take a small handful of the meatloaf mixture and place inside one of the onion layer pieces, then press another piece on top of the mixture, making an onion sealed meatball. Continue with the rest of your onion layers until your meatloaf mixture is gone. The number of onion bombs will depend on the size of the onions.
Wrap approximately 3 slices of bacon around each bomb. Secure the bacon with toothpicks so it does not unravel while it's cooking. Place on grill grates.
Smoke for 1 hour on the Traeger.
Increase the temperature 350F and cook for another 20-30 minutes until your internal temperature is around 160-165F. About 10 minutes before the bombs are ready, brush with your favorite Traeger BBQ sauce and allow it to caramelize. Remove from grill and allow to rest for 5 minutes. Enjoy!