Combine first 9 ingredients in a large bowl.
Cut bell peppers into large pieces, discarding seeds and membranes. Cut zucchini and onions into large pieces. Slice eggplant into 1/2-inch slices. Add vegetables to marinade; toss to coat. Cover and chill for 2 hours.
Remove vegetables from marinade, reserving marinade. Grill, uncovered, over medium-high heat (350º to 400º) 10 to 12 minutes or until just tender, basting occasionally with reserved marinade. Serve warm or at room temperature.