In a large saucepan, combine 1 qt. water, salt, brown sugar and peppercorns. Bring to a boil. Cook and stir until salt and sugar are dissolved. Remove from the heat. Add remaining cold water to cool the brine to room temperature.
Place a large resealable plastic bag inside a second plastic bag; add turkey breast. Carefully pour cooled brine into bag. Squeeze out as much air as possible; seal bags and turn to coat. Place in a pan. Refridgerate for 4-6 hrs. or overnight.
Prepare grill for indirect heat, using a drip pan. Meanwhile, combine basting ingredients. Place turkey over drip pan and grill, covered, over indirect medium heat for 1 1/4- 1 1/2 hrs. until meat thermometer reads 170°, basting occasionally with sauce. Cover and let stand 10 mins. before slicing.