Heat the oil in a large skillet over medium heat. Add the onion and garlic and cook until softened, about 3 minutes. Add the ground beef, breaking it up well with a spoon, and cook until the meat is cooked through. Pour off fat. Add
the tomato sauce, barbecue sauce, chili powder and crushed chilies and stir well to mix. Gently simmer 15-20 minutes, stirring occasionally. The mixture should be loose, with enough sauce to bind the meat. If it gets too thick, add a bit of water. Season with salt and pepper and then spoon onto hamburger buns and serve.