Combine teriyaki sauce, garlic powder, and honey. In large bowl toss chicken, bell pepper, onion, and pineapple with sauce. Cover with plastic wrap. Allow to marinate in refrigerator for 30 minutes.
Preheat oven to 420˚F. Spread oil over large baking sheet. Spread chicken and vegetables over pan. Cook for 15-18 minutes or until chicken reaches an internal temperature of 165˚F.
While chicken and veggies are cooking whisk together cornstarch, teriyaki sauce, and honey for glaze. Microwave for 30-60 seconds or until thickened. Drizzle sauce over chicken and veggies and top with green onions.