1. Preheat oven to 450°.
2. Combine soy sauce, ginger, and sesame oil, stirring well.
3. Cut 4 (12-inch) squares of aluminum foil; place a fish fillet in center of each square. Spoon green onions, bell pepper, and cucumber evenly over each fillet. Spoon soy sauce mixture evenly over vegetables. Fold foil over fillets to make packets, and seal edges tightly.
4. Place fish packets on a baking sheet; bake at 450° for 12 minutes.