In a small bowl, combine the cornstarch, water, barbecue sauce, hoisin sauce, soy sauce, ginger, garlic and salt until blended; set aside.
In a large cast-iron or other heavy skillet, saute onion and red pepper in oil until crisp-tender, 2-3 minutes; remove and set aside. In the same skillet, cook beef over medium heat until meat is no longer pink, 5-7 minutes, breaking into crumbles; drain.
Stir cornstarch mixture and add to the skillet. Bring to a boil; cook and stir until thickened, 1-2 minutes. Add coleslaw mix; stir to coat. Spoon meat mixture into the center of each tortilla; top with onion mixture. Roll up tightly.