1Heat gas or charcoal grill. In medium bowl, mix beef, onion and chiles. Shape mixture into 8 thin patties. Top each of 4 patties with 2 slices cheese. Place remaining beef patties on top; pinch edges to seal securely.
2Place patties on grill over medium heat. Cover grill; cook 14 to 16 minutes, turning once, until burgers are slightly firm when pressed in center. Add rolls, cut sides down, for last 4 minutes of grilling or until toasted. Serve patties on rolls with taco sauce.