Place potatoes in a large saucepan with cold water. Cook, uncovered for 15 minutes or until tender, adding the green beans for the last 5 minutes. Drain the potatoes and green beans. Refresh under cold water and set aside to cool for 10 minutes.
Meanwhile to make the dressing, combine the olive oil, white wine vinegar, salt and pepper in a screw-top jar. Close the jar and shake well to combine.
Pour over the dressing, add the parsley and toss gently to combine. Serve immediately – buon appetito.