Starting out as a Blacksmith to pay out his bills while pursuing amateur wrestling goals going on to win New Zealand's championship in 1949, 1950 before winning a silver medal in empire games, he entered professional wrestling in 1950 joining the NWA.
After putting in 5 years, he finally won the tag titles holding it on for a year before moving on to win British Empire heavyweight title of NWA dropping it to Gene Kiniski. He finally broke through in 1959 winning the NWA world heavyweight title from Dick Hutton. Due a lot of internal politics that involved money, he avoided the Chicago scene finally coming to a settlement taking on Bruno Sammartino, Johnny Valentine, Yukon Eric among others.
The TV boom came around this time allowing him to work for Vince Mcmahon Sr. eventually dropping the title to Buddy Rogers in front of 38622 in audience, a NA record that remained unbroken till 1986. It was dubbed as the Match of the Century and help Buddy Rogers break through as a heel when he pinned Pat who had missed a drop kick, injured his groin which Buddy Rogers capitalized. This match kick started the TV boom for wrestling.
Around this time AWA left NWA but Verne Gagne out of respect for Pat O'Connor's work dubbed him the first AWA champion making him hold both the titles from rival promotions simultaneously. He did not defend it and was stripped off the title eventually out of loyalty to NWA. Meanwhile, he went on to win tag titles twice from the likes of Harley Race, Larry Hennig before slowly disappearing from main event scene with the advent of TV era and Gimmick wrestlers taking the forefront.
Being credited as the best worker in the ring and as a well respected performer by friends and fans while playing a important role in transition of wrestling from live audience to TV era putting over and helping the likes of Buddy Rogers, Harley Race, Larry Hennig; he is a forgotten legend.