Fill a pot with just enough water to cover the potatoes, and bring it to a boil. Scrub the potatoes well if keeping the skins on, or peel them. Cut into quarters or sixths, depending on the size of the potatoes. Then place the potatoes into the boiling water and cook until they're just tender, but not mushy. When done, drain and run cool water over them. Set them aside until they're slightly warm or room temperature.

In a medium bowl combine the parsley, red onion, olive oil, white wine vinegar, garlic, and salt and pepper. Add the potato chunks and toss gently until well mixed. Let stand for 15 minutes at room tempertaure to allow flavors to blend. Serve at room temperature or chilled.