For a very juicy, tender chicken, use therotisserie attachment on your grill.
Heat oven to 325 degrees. Wash chickens inside and out with cold water and pat dry. Rub with oil and season inside and out with salt and pepper. Roast chickens on an oven rack until a meat thermometer reads 165 degrees, about 1 hour and 20 minutes. Don't allow chickens to brown.
Meanwhile, heat grill until medium hot, adding wood chips for a smoky flavor. Brush grill with oil. Remove chickens from oven and drain juices from cavity. Grill, covered, turning often, until golden brown on all sides, about 15 minutes. Carve and serve.