Combine salt, sugar, thyme, bay leaves, parsley, orange peels, if using, and 1/2 gallon of water in a pot over high heat.
Bring to a boil, then lower heat to simmer until sugar and salt are dissolved.
Remove from the heat, add the remaining water and let cool completely.
Place your turkey in a pot or other large container. Pour the brine over the turkey until it is completely submerged. Add more water if needed to cover the turkey.
Put entire container back in the refrigerator and let sit for at least 6 hours.
When ready to cook turkey, remove from brine and cook as usual.
