Step 1

Heat oil in a large skillet over medium-low heat. Add onion and garlic; cook and stir until onion is translucent, about 5 minutes. Add ground beef; cook and stir until browned, 8 to 10 minutes.

Step 2

Transfer beef mixture to a 6-quart slow cooker. Stir in kidney beans, diced tomatoes, tomato puree, water, green chile peppers, chili powder, salt, cumin, and black pepper.

Step 3

Cook on Low until flavors combine, 4 to 6 hours.