"I'm incredibly happy," O'Shea told Sky Sports News. "We felt coming up here that it was going to be an incredibly tough match. We knew they would fight tooth and nail for everything and anything they could get their hands on.
"Credit to our guys. To come here and get a win like that is huge for us, especially with the number of players we had missing."
Harlequins return to league action next Saturday when they welcome Exeter Chiefs to Twickenham Stoop.