1Heat closed medium-size contact grill for 5 minutes or to 375°F. Cut zucchini and summer squash in half lengthwise; with spoon, scoop out seeds and discard. Cut around stem of bell pepper to remove stem and seeds; cut bell pepper into quarters.
2Brush both sides of zucchini, squash and bell pepper pieces with oil; place on both sides of grill--do not close grill. Cook 4 to 6 minutes, turning once, until vegetables are tender. Remove from grill; let stand 2 minutes. Cut vegetables into 1-inch pieces.
3Spoon 2 teaspoons hummus onto each vegetable piece. Sprinkle with cheese; top each with 1 olive piece. Serve warm or cold.