In large saucepan or Dutch oven, combine potatoes, green beans and 2 cups water; bring to a boil. Reduce heat to medium; cook 10 to 12 minutes or until tender. Drain; rinse with cold water to cool. Drain well.
Meanwhile, in small bowl, combine all remaining ingredients except feta cheese; mix well.
Just before serving, place potatoes and green beans in serving bowl. Add vinegar mixture; toss gently to coat. Sprinkle with cheese.