Cut tin foil into 12X16 inch rectangle. Place green pepper, tomato and green onion on lower half of foil sheet. Sprinkle with 1/4 teaspoon basil, salt and pepper. Place fish on vegetables. Sprinkle with remaining basil, salt and pepper. Top with lemon slices. Fold upper half of foil over fish and vegetables. Double fold edges of foil to make a tight 1/2 inch seal. Place foil envelope on baking sheet and bake at 450F for 15 minutes or until envelope puffs. To serve, Cut an "X" in top of envelope and fold foil back.