Preheat the oven to 450ºF.
Arrange potatoes, lemon, onions, thyme and stock in a roasting pan. Drizzle with EVOO and season with grill seasoning. Arrange chicken pieces on top of the potatoes, drizzle with EVOO and season liberally with salt and freshly ground black pepper.
Transfer to oven and roast for about 30 minutes, until chicken piece reach an internal temperature of 165ºF.
While the chicken is roasting, throw together the Chimichurri: In the bowl of a food processor, add parsley, sage, oregano or marjoram leaves, shallot, garlic, red pepper flakes and red wine vinegar. Pulse to chop up the herbs then leave running while streaming in about 1/2 cup EVOO. Process to make a smooth paste. Season with salt and pepper, and reserve.