Begin by gathering all your ingredients. Chop the onion and slice the bell peppers if using. Rinse the kidney beans under cold water.

In a large skillet over medium-high heat, brown the ground beef for about 5-7 minutes until fully cooked. If using, add the onion for the last few minutes.

Transfer the beef and onion mixture to your crockpot. If not browning the beef, add it raw. Then, add the rinsed kidney beans, diced tomatoes, and chili seasoning.

Stir all ingredients together until evenly combined.

Place the lid on the crockpot and set it to cook on low for 6-8 hours or high for 3-4 hours.

Once done, remove the lid and stir the chili. Check seasoning and adjust if needed. Serve hot with desired accompaniments.