Combine kosher salt with brown sugar. If you do not have access to kosher salt, you can use 3 tablespoons of table salt instead. Mix in granulated garlic, onion powder, and black pepper to salt and sugar mixture.
Evenly apply the mixture all over the turkey, making sure to get under the breast skin.
Secure turkey into a large plastic bag; a large turkey cooking bag should work. Remove as much air as possible before sealing or tying the bag shut.
Place turkey in the refrigerator for at least 24 hours, turning every 8-12 hours or so.
Cook as directed.