Combine all ingredients in the Crock-pot and cook on high for 8-10 hours.
Once fully cooked, pour beans through a strainer to drain and retain 1/2 cup liquid to add back in if necessary.
Toss beans and veggie pieces back in the crock and mash with a potato masher, adding in some bean water if needed for consistency. For a smoother consistency process beans (and veggies) in a food processor or with an immersion blender.
Serve immediately as a side or in your favorite Mexican dishes.
Store in an airtight container for 5 days or freeze for up 3 months.