Preheat Traeger grill to high heat and preheat a cast-iron Dutch oven in the grill until very hot. Sauté onion in a few tablespoons of oil, until translucent.
While you sauté the onion, place the sausage next to the pan on the grill and allow to cook. Add chopped meats to sautéed onions and cook, stirring frequently, until browned all over.
Pour chicken broth into Dutch oven and deglaze the pan. Use a wooden spoon to free the browned bits from the bottom of the pan. Bring to a simmer and stir in drained beans and BBQ sauce. Cut the cooked sausage into slices and stir into mixture.
Allow to cook for 45 minutes, stirring occasionally, while the sauce reduces. Place stale bread on the grill and toast until brown and very dry. Cool and then tear into large bread crumbs.
When the meat/bean mixture has cooked for about an hour and thickened, stir one more time and then cover the surface with bread crumbs. Cook for 15 minutes more, then remove from grill and allow to cool briefly.
Serve as-is, or spooned over pasta. Sprinkle with cheese if desired.