In a large skillet over medium heat, add the lean ground beef and brown for 4–5 minutes, breaking it into small pieces until no longer pink.

Introduce the diced onion and continue cooking for an additional 4–5 minutes until the onion is soft and translucent.

Once the onions are tender, stir in minced garlic and sprinkle the chili powder, cumin, garlic powder, oregano, salt, and black pepper. Cook for about 30 seconds.

Carefully pour the sautéed mixture into a 6-quart slow cooker.

Next, stir in the drained black beans and kidney beans, along with the undrained diced tomatoes and tomato sauce.

Cover the slow cooker with its lid and set it to cook on high for 3–4 hours or on low for 6–8 hours.

When the cooking time is up, taste the chili and adjust seasoning as needed.