Preheat oven to 425°.
Combine first 4 ingredients in a large heavy-duty zip-top plastic bag. Add zucchini, onions, and eggplant; seal and shake to coat. Arrange vegetables in a shallow roasting pan coated with cooking spray. Lightly coat vegetables with cooking spray. Bake at 425° for 20 minutes; drizzle with vinegar. Bake an additional 20 minutes or until vegetables are tender. Combine vegetables, peppers, parsley, and olives, tossing well.