In a small bowl, mix the teriyaki sauce, oyster sauce, 1 tablespoon cornstarch, rice vinegar, and sesame oil until well blended. Set aside.
Heat the canola oil in a nonstick wok over medium-high heat. Toss the halibut in the remaining cornstarch and add to hot oil. Sear quickly on all sides, about 3 minutes total. Remove halibut from wok and set aside. Add broccoli, snow peas, bell pepper, and ginger to the wok with 1/4 cup of water and cover. Steam vegetables until crisp tender, about 3 minutes. Add teriyaki sauce mixture and stir until the vegetables are well coated. Simmer over low heat until sauce thickens. Once sauce has thickened, return halibut to the wok and cook until warmed through. Serve immediately.