It is fitting recognition for Harley who left Glasgow Warriors at the end of the season after a record 267 appearances for the club across 12 years.
Harley, who has now signed for French Pro D2 side Carcassonne, is the sole Scot in the Baa-Baas squad which will be coached by former Cardiff chief John Mulvihill.
Barbarians hammered England 52-21 at Twickenham last weekend but this is an entirely different selection which will be captained by Welsh centre Hadleigh Parkes.
Other notable inclusions for the game on Saturday (8pm kick-off, UK time) are Ireland’s Devin Toner, Samoa’s Rey Lee-Lo and Wales’ James Botham, the grandson of England cricketing great, Ian.
Barbarians president John Spencer said: “The club is buzzing after a wonderful victory over England on Sunday and this new squad, coached by John, is excited to take up the reins and embody the Barbarians’ ethos and playing style: spirit, passion, courage and flair, united by lifelong friendship.”