The players will train for an hour from 7:30pm and will then spend time signing autographs ahead of the big game.
London Wasps have tasted European success on three previous occasions, lifting the Heineken Cup in 2004 and 2007 as well as their triumph in the Amlin Challenge Cup in 2003.
Victory over Toulouse in the last round of Pool action in this year's Heineken Cup secured Wasps a place in the Amlin Challenge Cup knock-out stages as one of three runners-up.
Harlequins will be looking to lift the Amlin Challenge Cup for the third time this season after winning the competition in 2001 an 2004. They made it through to the quarter-final stage after finish top of Pool 1.