Rinse beans and sort, if necessary, discarding any blemished ones and any grit.
In large Dutch oven or stockpot, cover beans with 3 times their volume of water. Bring to boil; boil gently for 2 minutes. Remove from heat; cover and let stand for 1 hour. Drain, discarding liquid.
Return soaked beans to pot along with 3 times their volume of fresh water. Bring to boil; reduce heat and simmer, covered, for 30 to 45 minutes or until tender. Drain, reserving 2 cups (500 ml) cooking liquid.
Meanwhile, dice bacon; set aside. In bowl, and using potato masher, mash tomatoes in their juice.
In bean pot or 16-cup (4 L) casserole, combine beans, reserved cooking liquid, bacon, tomatoes, onions, dried oregano, cumin, taco sauce, molasses, sugar, mustard, salt and pepper.
Bake, covered, in 300ºF (150ºC) oven for 2-1/2 hours. Stir in chopped sweet green or red peppers. Uncover and bake for 1 to 1-1/2 hour longer or until sauce is thickened and coats beans well.