Peel eggplant; cut in half lengthwise.
Cut each half crosswise into 1/2-inch-thick slices.
Combine eggplant, squash, and next 7 ingredients 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.