Place peppers on grill rack; grill 15 minutes or until charred, turning occasionally. Place peppers in a zip-top plastic bag; seal and let stand 15 minutes. Peel peppers; discard seeds and membranes. Coarsely chop peppers; place in a large zip-top plastic bag. Place zucchini and eggplant on grill rack; grill 10 minutes, turning occasionally. Remove zucchini and eggplant from grill; let stand 10 minutes. Coarsely chop zucchini and eggplant; add to chopped peppers.
Combine parsley and remaining ingredients, stirring with a whisk. Pour the parsley mixture over pepper mixture. Seal bag; toss gently to coat. Refrigerate at least 2 hours or overnight.