Grill fish 5 min.; turn. Add remaining lemon slices and asparagus to barbecue. Grill 5 min. or until fish flakes easily with fork and asparagus is crisp-tender, brushing occasionally with remaining dressing mixture. Remove fish, lemon slices and asparagus from barbecue. Discard lemon slices under fish. Serve remaining lemon slices with the fish and asparagus.