Dice onion and bell pepper and sauté in oil over low-medium heat until tender.
Meanwhile, measure out 2 cups of dry pinto beans. Inspect for and remove any rocks and debris. Rinse under cold water.
Combine beans, water, onion, pepper, and the remaining ingredients in a slow cooker.
Cover and cook on high for 4 hours and then either let cooker continue on “warm” if left overnight or set to low until cooked (approx. 4 hours more).