Combine the olive oil, vinegar, prunes, olives, capers and juice, bay leaves, garlic, oregano, salt and pepper in a large bowl. Add the chicken and stir to coat. Cover the bowl and refrigerate overnight.
Preheat oven to 350. Arrange chicken in a single layer in one or two large, shallow baking pans and spoon the marinade over evenly. Sprinkle the chicken pieces with the brown sugar and pour the white wine around them. Bake, basting frequently with the pan juices, until the thigh pieces yield clear yellow (rather than pink) juice when pricked with a fork, 50 minutes to 1 hour.
With a slotted spoon, transfer the chicken, prunes, olives and capers to a serving platter. Moisten with a few spoonfuls of the pan juices and sprinkle generously with the parsley or cilantro. Pass the remaining pan juices in a sauceboat. Serves 10 or more