"I'm delighted with the result - it's an away win," BBC Sport quotes O'Shea as saying. "We played two games against them last season and they were both decided by a score - this was decided by a post.
"I had mentally prepared myself for it to go over. He hit it beautifully and it hit the post - it's hit the inside of the post, not even the fat side.
"I said to Dai [Young] after the game we just shouldn't play each other, it's horrible."
Quins play their first home match of the season on Friday when they welcome Northampton Saints to Twickenham Stoop.