Place beans in a large saucepan; add water to cover by 2 in. Bring to a boil; boil for 2 minutes. Remove from the heat; cover and let stand for 1 to 4 hours or until beans are softened. Drain and rinse beans, discarding liquid.
In a large kettle or Dutch oven, simmer beans and beef in water for 2 hours or until very tender; drain. Place beef and beans in a 5-qt. slow cooker.
In a large skillet, cook bacon over medium heat until crisp. Using a slotted spoon, remove bacon to slow cooker. Discard all but 3 tablespoons drippings. Saute the onion, carrots, celery and peppers in drippings until tender. Add garlic; cook 1 minute longer. Transfer to the slow cooker. Add all the remaining ingredients except buns. Cover and cook on high for 3-4 hours, stirring often. Discard bay leaf. Spoon 1/2 cup onto each bun.