Olly joined Harlequins from Bristol in July 2006 and made his debut in the pre-season friendly with ASM Clermont that summer. He has since made 135 appearances for the current Premiership champions and has scored four tries.
"We are delighted that Olly has been called into the Wales squad and look forward to him receiving a first international cap in the forthcoming Six Nations Championship," said Harlequins Director of Rugby Conor O'Shea.