Wash beans, and remove any foreign particles and debris.
Soak beans in water to cover in a 6-quart stockpot 8 hours. Rinse and drain beans.
Bring beans, 3 quarts water, and bouillon to a boil. Cover, reduce heat to low, and simmer 3 hours. Do not drain.
Process 1/2 small onion and bell pepper in a blender or food processor until smooth, stopping to scrape down sides.
Sauté garlic in hot oil in a large skillet over medium-high heat 1 minute. Add onion mixture, and cook, stirring constantly, 4 minutes.
Stir onion-and-garlic mixture into beans. Add oregano and next 4 ingredients. Simmer, uncovered, 1 1/2 to 2 hours or until beans are tender and soup is thick. Garnish, if desired.