1. Heat oil in a Dutch oven over medium heat. Add garlic and onion; sauté 5 minutes or until tender. Add cumin and chili powder; cook 1 to 2 minutes, stirring constantly (mixture will adhere to pan). Stir in beans and next 3 ingredients, scraping pan to loosen browned bits; bring mixture to a boil. Reduce heat, and simmer 30 minutes.
2. Stir in bell pepper; simmer, uncovered, 10 minutes. Ladle soup into individual bowls. Top each with sour cream and green onions.