Mix melted butter, soy sauce, rice vinegar and brown sugar in a small bowl; set aside.
Mix remaining ingredients in a large bowl.
Place half the veggie mix in center of sheet of foil. Spoon half the butter mixture over veggies.
Bring up sides of foil over veggies; fold down two times. Double fold both ends of foil to seal packet, leaving room for heat circulation inside. Repeat to make second packet.
Place packets on baking sheet with 1-inch sides.
Bake 15 to 20 minutes or until veggies are desired crispness. Open packets carefully by cutting along top folds with a sharp knife, allowing steam to escape. Stir to coat evenly.