1. Heat grill. Gently combine ground beef and rosemary in medium bowl. Divide beef into quarters, then gently shape each piece into a 1/2- to 3/4-inch-thick patty.
2. Sprinkle both sides of burgers with salt and pepper. Grill burgers 7 to 8 minutes. Turn and grill 7 minutes more, or until instant-read meat thermometer reaches 160 degrees F when inserted 1 inch from edge of each burger (for medium).
3. Meanwhile, for the tartar sauce combine mayonnasie, dill pickles and shallots in small bowl. Divide and spread sauce on bottoms of rolls. Top with watercress, burgers, tomato, and tops of rolls. Serve with potato chips, if desired. Makes 4 servings.