PREHEAT both burners of gas grill to medium-high heat. Trim the excess fat from the chickens and discard. Cut lemons in half; squeeze juice into a small bowl. Reserve lemon halves for later use. Add barbecue sauce and seasoning to the lemon juice; mix well.

PLACE 2 each of the lemon halves and garlic cloves inside the cavity of each chicken.

TURN off the burner on one side of the grill, then place the chickens, breast sides up, on that side. Cover grill with lid. Grill 1-1/2 to 2 hours or until the chicken juices run clear and a meat thermometer inserted into the thickest part of the thighs registers 180°F, occasionally turning and brushing the chickens with the barbecue sauce mixture during the last 20 min. of the grilling time. Remove and discard lemon halves and garlic cloves from chicken cavities before serving.