In small bowl, whisk together vinegar, pesto, oil and pepper; set aside.
In large bowl, combine couscous with 3/4 cup (175 mL) boiling water; cover and let stand for 5 minutes. Fluff with fork; fold in chickpeas and green onion.
Cut eggplant and zucchini lengthwise into 1/4-inch (5 mm) thick slices. Place eggplant, zucchini and yellow pepper on greased grill over medium-high heat; close lid and grill, turning once, until tender-crisp, about 10 minutes. Alternatively, you could also broil the eggplant, zucchini and yellow pepper on a baking sheet until tender-crisp.
Cut eggplant and zucchini into 1-inch (2.5 cm) wide strips. Cut pepper into 1-inch (2.5 cm) cubes. Add grilled vegetables and tomatoes to couscous. Add pesto mixture; toss to combine.