Mr Lawn is looking for fans and staff to get into the festive fundraising spirit for the game at the Coral Windows Stadium against the current league leaders Burton (kick off 3:00pm).
The idea behind the onesie challenge is to help raise funds for Cancer Research on behalf of Mark's wife Yvonne, who has terminal cancer.
The club would love to see fans getting sponsored by family and friends to wear their onesie for the Burton fixture.
Pledges for the charity onesie challenge can be made at www.justgiving.com/bcafc