1.In a pot bring 1 quart of water to a simmer over medium-low heat add in the sugar and salt. Stir until ingredients are fully dissolved. Remove from heat to cool slightly.
2.Add remaining 3 quarts of cold water into a large bowl, along with the rosemary, thyme, peppercorns, and garlic. Pour in the warm sugar/salt water and stir to combine. To cool the brine completely, add the ice and stir until brine is fully chilled.
3.Put the turkey and brine into a brining bag or container large enough to hold the turkey and all the liquid. Allow the turkey to brine in the refrigerator for 1 or 2 days. Remove turkey from brine 1 hour before cooking, rinse quickly and pat dry. Let turkey come to room temperature before roasting.