The 50-year-old joins the Robins following spells coaching at Gillingham, Portsmouth, Plymouth and Stoke.
O'Connor told the club's official website: "I'm looking forward to the challenge. The main thing for me was to be back in work and it's a great opportunity, one I plan to grab with both hands.
"I played with Sean (O'Driscoll) at Bournemouth for many years and I had great respect for him as a player. We've kept in touch ever since and I was delighted when he asked if I'd be interested in working with him.
"I worked with the youth teams at Portsmouth for six or seven years and I've always liked working with young players.
"Sean spoke a lot about investing in youth and wanting close links between the youngsters and the first team, which was obviously very pleasing to hear."