Mix meat, onions and half the chipotle peppers just until blended; shape into 4 (1/2-inch-thick) patties. Stir remaining chipotle peppers into barbecue sauce.
Brush half the barbecue sauce mixture evenly onto cut sides of buns.
Grill patties 8 min.; turn.
Brush with remaining barbecue sauce. Grill 4 min. or until burgers are done (160F). Top burgers with cheese and place buns, cut sides down, on grill grate; grill 1 min. or until cheese is melted and buns are lightly toasted.
Fill buns with lettuce, tomatoes and cheeseburgers.