In a small bowl, whisk the first 10 ingredients. Refrigerate until serving., Cook couscous according to package directions. Meanwhile, brush the zucchini, yellow peppers and eggplant with oil; sprinkle with salt and pepper. Grill, covered, over medium heat until crisp-tender, 10-12 minutes, turning once., Chop grilled vegetables; place in a large bowl. Add the tomatoes, olives, parsley, basil and couscous. Pour dressing over salad and toss to coat. Serve warm or chilled.