1) Combine Ground Beef and seasoning ingredients in large bowl, mixing lightly but thoroughly. Shape into six 1/2-inch thick patties. Place patties on grid over medium, ash-covered coals. Grill, covered, 8 to 10 minutes (over medium heat on preheated gas grill, 7 to 9 minutes) until instant-read thermometer inserted horizontally into center registers 160°F, turning occasionally. 2) Meanwhile, combine sauce ingredients in small bowl; set aside. 3) Spread sauce on cut sides of rolls. Place one burger on bottom half of each roll; top evenly with watercress. Close sandwiches.
Cooking times are for fresh or thoroughly thawed Ground Beef. Color is not a reliable indicator of Ground Beef doneness.