1In tightly covered container, shake all Tarragon Dressing ingredients.
2Cut beans in half if desired. In 2-quart microwavable casserole, place beans, potatoes and water. Cover and microwave on High 10 to 12 minutes, rotating casserole 1/2 turn every 4 minutes, until potatoes are tender; drain.
3In large glass or plastic bowl, toss beans, potatoes and dressing. Add onion and bell pepper; toss. Cover and refrigerate 1 to 2 hours or until chilled.