Wash nopalitos, watch for small thorns, use potato peeler to smooth over and remove sprouting thorns. Cut nopalitos into small cubes, wash again, drain. Set aside.
Brown steak in oil after you have cut it into 1/2 inch cubes. Use large skillet. Remove cubes with slotted spoon as they brown. Add onions, green peppers and garlic; saute stirring often, until tender. Add nopalitos to mixture, cook 3 minutes. Sprinkle chili powder over mixture; cook and stir one minute.
Return meat to skillet; add tomatoes, water, salt and oregano; bring to boiling. Lower heat; cover; simmer 30 minutes, stirring occasionally.
Drain beans, reserving about half the liquid. Add beans and reserved liquid to skillet; simmer, uncovered, 15 minutes.