Jonathan Thurston inspired the second-half comeback, scoring once and having a hand in the other two tries as the Cowboys edged Newcastle 20-18.
Coen Hess and Thurston scored within three minutes of each other early in the second half, but with Ken Sio more accurate with his conversions, the hosts were still behind until the dramatic late try.
The exciting finish was in stark contrast to the way the Cowboys started. After two minutes Jack Cogger drew Thurston then played in Fitzgibbon who burst through a big gap before darting inside Te Maire Martin for the Knights to open the scoring.
The second try saw Danny Levi take the play the ball two metres out and feed Aidan Guerra who broke the line untouched.
The Cowboys were allowed back into the game at the midpoint of the first half when Levi was sent to the sin bin.
And within two minutes they were on the board as a run-around between Thurston and Cooper led to the Cowboys captain finding O’Neill alone on the touchline for an easy try.
The lead was restored seven minutes before the break when Fitzgibbon scored again, bursting through a gap and brushing off despairing tackles between Thurston and Kane Linnett.
After stinging words from Paul Green, the Cowboys came out a better side and Thurston found Hess on the right flank and he burst through two tackles to reduce the margin to eight points.
The Cowboys scored again when Thurston went wide to Linnett who passed to O’Neill and his smart kick inside bounced perfectly for his skipper to collect.
As time was running out and with the Cowboys staring at a sixth-straight defeat, Thurston found Martin who passed to Cooper for the winning points.