Peel eggplant; cut in half lengthwise. Cut each half crosswise into 1/2-inch-thick slices. Combine eggplant and next 8 ingredients (eggplant through onion) in a large zip-top plastic bag; seal, and marinate at room temperature 45 minutes, turning bag occasionally. Remove vegetables from bag, reserving marinade.
Thread vegetables alternately onto 2 (10-inch) skewers. Prepare grill or broiler. Place kebabs on grill rack or broiler pan coated with cooking spray; cook 6 minutes on each side or until done, basting occasionally with reserved marinade.