Bournemouth bounced back from the shock of falling behind after just seven seconds to a goal from Matt Fryatt to secure their third win in the last five games.
Steve Fletcher's seventh goal of the season had put Bournemouth on level terms before O'Connor struck eight minutes into the second half with a 25-yard free-kick.
While Bournemouth are chasing promotion, Walsall are in free fall.
They have failed to win any of their last five games and have taken only two points from the last 15.
They could not have made a better start as Fryatt raced on to a pass from Michael Standing and powered past three Bournemouth defenders before sliding the ball beyond goalkeeper Neil Moss for his 13th goal of the season.
Bournemouth took some time to get over that setback and Walsall would have moved further ahead but for Moss saving well from Jorge Leitao.
When they did work their way into the game, Bournemouth began to seriously test Walsall's teenage goalkeeper Dean Coleman who was making his full debut.
Coleman had to dive full length in the 17th minute to turn away a shot by Wade Elliott before Ian Roper turned James Hayter's follow-up off the line.
Impressive Walsall midfielder Michael Standing did give Bournemouth a scare when his cross-shot hit the bar but it was no real surprise when the Dean Court side forced their way back on to level terms five minutes before half time.
Walsall failed to cut out a long right wing cross from Elliott which Hayter headed back into the path of Fletcher. The powerfully built marksman then fired the ball over Coleman and into the roof of the net from six yards.
Coleman was left just as helpless in the 53rd minute when O'Connor made his decisive contribution.
The Irishman won the free-kick when he was fouled by Simon Osborn and then picked himself up to drill his powerful shot beyond Coleman to score for the 12th time this season.
Falling behind sparked Walsall into their best spell of the game but they could not find a way past Moss who pulled off impressive saves from Taiwo Atieno and Fryatt to seal Bournemouth's victory.