Heat the oil in a wok or large skillet set over medium-high. Add the scallops and cook 1 minute per side, or until just cooked through. Remove the scallops from the pan and set them aside. Add the mushrooms to the pan and stir-fry for 2 minutes. Add the garlic, ginger, bell pepper and snow peas and stir-fry 2 minutes more. Add the teriyaki sauce and cornstarch/water mixture and bring to a simmer. Return the scallops to the pan and cook until just heated through. Season with pepper and serve.