The East Coast Sprint Series is a three round tour of Queensland with rounds at Cairns Speedway, Mackay Speedway and the Toowoomba Speedbowl.
Lack's consistency over the three rounds saw him take the series win after finishing on the podium in the final two events.
Fellow Lucas Oil driver McFadden recorded race wins at Mackay and Toowoomba after joining the series in round two.
McFadden started third in the final race at Toowoomba and muscled his way to the front before driving away from the field.
A red light stoppage with 13 laps to go saw rain roll in and McFadden declared the winner.