To a large skillet, add oil and heat over MED to MED-HIGH heat. Add onions and bell pepper and cook, stirring occasionally, until softened and very fragrant, about 5 minutes.
Add ground beef and cook about 5 minutes, crumbling with a wooden spoon or potato masher, until beef is no longer pink. Drain any excess fat, and return beef mixture to skillet.
Add salt, chili powder, cumin and black pepper and minced garlic, and cook about a minute.
Transfer beef mixture to the bottom of slow cooker. Add crushed tomatoes, tomato sauce, beans and green chiles, and stir well to combine. Cover and cook on LOW for 8 hours, or on HIGH for 5-6 hours.
Taste chili and season with salt and black pepper if needed. Serve with any desired toppings and enjoy!