In search of his 38th ranking title and second in the event, O'Sullivan rattled off four frames running having lost the opener, signing off with breaks of 107 and 81.
O'Sullivan had lost 5-0 when the pair met in German Masters qualifying earlier this year, but after levelling the scores was never in any real danger despite missing several chances before finding his stride late on.
Clearly, there was room for improvement and O'Sullivan said: "There’s no enjoyment stinking gaffs out like that, that was horrendous. If I was to play like that, you have to be honest with yourself, I’m not going to get any better now, I know when to throw it in because I didn’t enjoy that."
Next for O'Sullivan is a meeting with Jimmy Robertson, who came from behind three times in a 4-3 victory over in-form Luca Brecel.
Brecel can lay claim to being the hottest player in the sport, having won the Scottish Open on Sunday and lost in the final of the UK Championship a week earlier, but failed to capitalise having led 1-0, 2-1 and 3-2, as Robertson secured a notable scalp.
Later in the afternoon, Stephen Maguire came from 3-1 down to beat Jack Lisowski 4-3 and could meet O'Sullivan in the semi-finals.
On the other side of the draw both semi-finalists are known, after contrasting wins for Mark Selby and Neil Robertson.
Selby was a comfortable if not totally convincing 5-2 winner against Tom Ford, whose run of giant-killings came to an abrupt end after he'd defeated John Higgins and Judd Trump earlier in the week.
Robertson on the other hand won a tense deciding frame to beat Yan Bingtao 5-4.
Yan broke down when among the balls in the decider, missing a medium-length red, but Robertson's counter-punch ended when he missed a tricky red with the rest.
Yan was unable to capitalise though, a poor positional shot from green to brown ending his break, before Robertson's thin blue proved decisive at the end of a long safety exchange.
