In a large skillet over medium-high heat, cook the chopped bacon until it is crispy. Use a slotted spoon to remove the bacon from the skillet and set it aside on a paper towel-lined plate.

Add the ground beef and chopped onion to the same skillet with the bacon grease. Cook until the beef is fully browned and the onion is soft, breaking up the meat with a spoon. Drain any excess fat from the skillet.

Transfer the cooked beef and onion mixture to the basin of a 6-quart or larger slow cooker. Add the minced garlic, undrained pinto beans, undrained kidney beans, BBQ sauce, brown sugar, apple cider vinegar, Worcestershire sauce, and half of the crispy bacon. Stir until all ingredients are well combined.

Cover the slow cooker and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, until the sauce is thickened and bubbly.

Stir the cowboy beans one last time before serving. Garnish with the remaining half of the crispy bacon. Serve hot.