Mix beef, onion, ketchup, Worcestershire sauce, salt, and pepper in a bowl. Shape into eight 3-inch diameter 1/4-inch-thick patties. Place 1/4 cup cheese in the center of four patties; top with remaining patties. Press edges firmly to seal; refrigerate for at least 15 minutes.
Heat an outdoor or indoor grill to medium; oil the grill grate. Grill burgers, covered, over medium heat for 5 to 6 minutes on each side or until meat reaches desired doneness.
Place the Fresh Express® Bacon Thousand Island Chopped Kits® into a large bowl; toss with the salad dressing. Add the toppings; toss to combine.
Serve hamburgers on buns topped with the Bacon Thousand Island Chopped Kit® and other traditional toppings as desired.