1. Sauté onion, bell peppers, and garlic in saucepan with a little water or vegetable broth over medium heat 2 to 3 minutes, or until vegetables soften.
2. Transfer to blender, and purée until smooth. Add 3 cups cooked beans and 6 to 7 cups water; purée until mixture is consistency of thick soup.
3. Return mixture to saucepan, and add remaining beans, potatoes, vinegar, cumin, oregano, bay leaf, and salt. Bring to a simmer.
4. Reduce heat to medium-low, and simmer, covered, 20 minutes, or until potatoes are soft. Remove bay leaf. Garnish each serving with diced red onion and green bell pepper