PREHEAT: grill to medium - high heat. Meanwhile, soak 4 wooden skewers in water. Toss shrimp with 1/4 cup of the dressing. Let stand 10 min. to marinate. Drain; discard marinade. Place shrimp evenly on skewers.
LAYER: 3 (14-inch) squares of foil. Fold foil in half. Double fold the 2 opposite sides to make pouch. Place rice, zucchini and peppers in pouch. Gradually add chicken broth and remaining 1/4 cup dressing. Double fold foil at top of pouch to seal, leaving room for air to circulate inside pouch.
PLACE: foil packet on grate of grill; cover grill with lid. Grill 10 to 15 min. or until most of the liquid has been absorbed. Let stand 5 min. Meanwhile, place skewers on grill. Grill 5 min. or until shrimp turn pink. Place rice mixture on serving platter; top with shrimp. Sprinkle with onions.