In a skillet, brown ground beef with half of the diced onion. Cook until beef is fully cooked. Drain off any excess grease.
Add chili beans along with ¼ cup bbq sauce to beef mixture. Stir to combine. If needed add additional bbq sauce to reach desired consistency. You want it thick enough to serve on buns.
Serve mixture on top of buns topped with shredded cheese and the remaining diced onion.