For the brine, heat ingredients in a saucepot to dissolve sugar and salt then cool completely.
Place turkey in 2.5-gallon plastic bag and add brine. Let rest several hours, preferably overnight.
If using a conventional oven, set turkey on a metal rack set on a rimmed baking sheet and preheat oven to 325ºF. Pat the turkey dry, rub with oil and season with ground pepper. Roast 15 minutes per pound.