Thread vegetables evenly onto 12-inch skewers.
Stir together melted butter, basil, and garlic powder; reserve 1/4 cup butter mixture, and set aside.
Coat food rack with cooking spray; place on grill over medium-high heat. Place vegetables on rack.
Grill, covered with grill lid, 20 to 25 minutes or until vegetables are tender, turning and basting with remaining butter mixture every 5 minutes. Serve with reserved butter mixture. Prep: 20 min., Grill: 25 min.