Cut each potato in half lengthwise; quarter each potato half. Steam potatoes, covered, 13 to 15 minutes or until tender.
While potatoes cook, combine oil and next 5 ingredients in a large bowl; stir well. Drain potatoes. Add warm potatoes to bowl; toss gently to coat. Sprinkle with parsley, chives, and tarragon just before serving. Serve warm or at room temperature.