Place potatoes large saucepan. Add water to cover. Bring to boil. Cook 5 to 6 minutes or just until potatoes are tender. Add green beans; cook 2 minutes. Drain.
Toss potatoes, beans, olives, celery and onion in large bowl. Mix remaining ingredients in small bowl with wire whisk. Add to vegetables; toss to coat. Cover.
Refrigerate 4 hours or until ready to serve. Toss before serving.