Whisk together water, salt, sugar, garlic and rosemary until salt and sugar dissolves.

Place chicken in a one gallon resealable plastic bag. Place bag inside a large bowl.

Pour brine over the top of chicken, seal and refrigerate for at least 2 hours but not more than 4.

Prepare grill for indirect heat and heat to 425 degrees.

Rinse and pat dry the chicken. Season both sides liberally with salt and pepper.

Cook chicken skin side down, for 5 minutes. Reduce heat down to 350. Continue cooking chicken for 10 minutes or until it easily releases from the grill. Flip and continue cooking for another 10 - 15 minutes or until a meat thermometer inserted reads 165 degrees and the juices run clear.

Transfer to a plate, sprinkle with fresh rosemary, if desired, serve.