1. Combine first 4 ingredients in a large bowl, stirring with a whisk. Add cucumbers to bowl, tossing to coat. Cover and marinate in refrigerator 1 1/2 hours.
2. Prepare grill to medium-high heat.
3. Remove cucumbers from bowl, reserving marinade. Arrange cucumbers in a single layer on grill rack coated with cooking spray; grill for 2 minutes, brushing cucumbers with reserved marinade. Turn cucumbers over, and grill for 3 minutes or until browned, brushing with reserved marinade.
4. Sprinkle cucumbers with sesame seeds and pepper. Serve immediately.