He made his professional debut as a referee for Frank Ducey, the matchmaker for the Casino Athletic Club of Lynn, Massachusetts.
In 1920 he refereed the first ever bout regulated by the Massachusetts Boxing Commission - a fight between welterweights Nate Siegal and Paddy Flynn.
[2] In 1924, Lawrence J. Sweeney of The Boston Globe questioned O'Connor's decision to declare Quntion Romero-Rojas victorious over Jack Renault.
[6] On April 2, 1928, O'Connor declared Roberto Roberti victorious over Ted Sandwina as a result of a foul in the third round of their fight at Mechanics' Hall.
[9] On December 13, 1929, O'Connor stopped a fight between welterweight champion Jackie Fields and Gorilla Jones in the seventh round.
[11] On September 17, 1937, O'Connor refereed a bout between the undefeated Ralph Zannelli of Providence, Rhode Island, and Peter Jackson of Los Angeles.
[12] Other notable bouts officiated by O'Connor include Joe Tiplitz vs. Johnnie Downs, Tommy Gibbons vs. Pat McCarthy, Hambone Kelly vs. George Robinson, Jack Britton vs. Frankie Schoell, Sully Montgomery vs.
[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][excessive citations] In 1911, O'Connor joined the survey and design section of the Boston public works department's highway division as a rodman.