McPake secured the win with his 74th-minute goal, but was stretchered off five minutes from time after a clash with Scott Wilson.
Dunfermline's miserable day was summed up when substitute Gjorgi missed a glaring chanced in the closing stages. By then, the Dunfermline fans were calling for the head of manager Davie Hay as they are now deeply in the mire.
Livingston keeper Roddy McKenzie had to be alert in the opening exchanges as he kept out a fiercely-struck shot from Darren Young. Billy Mehmet then had a great chance for Dunfermline when he was unguarded at a Lee Makel free-kick, but his 10-yard header spun wide.
Livingston hit back and Hassan Kachloul almost caught out Derek Stillie with a quick free-kick, but the goalkeeper flopped to his right to prevent the ball from slipping in at the corner of his net. O'Brien then came close with a left-foot shot from 20 yards which was just a foot wide of the post.
Livingston's Derek Lilley should have opened the scoring after an intelligent pass from Kachloul set him up, but he rushed his effort and it finished well over the top.
Andrius Skerla came to Dunfermlijne's rescue after 27 minutes when he made a last-ditch header to prevent Colin McMenamin getting his head to a David McNamee cross in the six-yard box. But it was by no means one-way traffic. McKenzie was well positioned to save a curling free-kick from Makel.
At the other end, Stillie had to dive full-length to push a McMenamin shot for a corner.
The breakthrough came after 33 minutes. McMenamin sent O'Brien clear and, as Stillie advanced, he kept his cool to notch his eighth goal of the season. Dunfermline tried to respond, but too often were let down by a poor final pass into the area.
Mehmet came closest a minute from the break with a flashing header from a Makel cross, but again McKenzie's positioning was perfect as he held the ball under his crossbar.
Livingston continued to look the more dangerous in the second half, and Stillie did well to hold a sweetly-struck volley from Jason Dair.
Dunfermline threw everyone forward in the closing stages, but they were hit with a sucker punch 16 minutes from time. McPake scored from close range after McMenamin had helped on an O'Brien corner.