Brown the ground beef in a large dutch oven over medium-high heat.
Add the onions and red bell pepper and cook for another 5 minutes.
Drain excess fat if necessary and transfer to a slow cooker.
Add the black beans, corn, tomatoes, beef broth, mild green chilies and taco seasoning.
Stir to combine.
Cook over low heat for 6 to 8 hours.
Notes
Storage
Slow cooker taco soup can be stored in an airtight container in the refrigerator for up to four days. For longer storage, you can also keep it in the freezer for about three months.