Preheat oven to 220C/Gas 7.
1) Whisk olive oil, lemon juice, shallots, garlic, oregano, and parsley in a medium bowl to blend; season with salt and pepper to make a vinaigrette.
2) Toss potatoes with 125ml vinaigrette on a heavy, large, rimmed baking tray. Reserve the remaining vinaigrette.
3) Pour chicken stock around potatoes and season potatoes with salt and pepper. Roast potatoes until tender and golden brown, turning occasionally, about 45 minutes.
4) Transfer to a serving platter and drizzle with the remaining vinaigrette and more chopped parsley.