In a large skillet, heat oil over medium-high heat. Add onions; cook and stir until tender. Add garlic; cook 1 minute longer.
Transfer to a 3-qt. slow cooker. Stir in chicken, beans, stock, chilies and dry seasonings.
Cook, covered, on low 6-8 hours or until heated through. Stir in cilantro. If desired, serve with corn chips, cheese and sour cream.