In 1951, O'Connor turned professional with Tuam members funding his first tournament at the Open Championship at Royal Portrush, Antrim that same year.

[2] Throughout the 1960s he won at least one professional event during each year on the British Tour, a level of consistent success matched by very few other players.

His best performance came at the 1965 Open Championship where O'Connor tied for second place with Brian Huggett, two behind five-time winner Peter Thomson.

[4] He easily outplayed international stars like Jack Nicklaus, Arnold Palmer, Sam Snead, and Gary Player.

[5] O'Connor played in every Ryder Cup from 1955 to 1973, setting a record of ten appearances in the event which stood until it was surpassed by Nick Faldo in 1997.

He was the Irish professional champion on ten occasions, including in 1978 (when he was 53), and was twice (1961 and 1962) recipient of the Vardon Trophy for leading the British Tour's Order of Merit.

In 1970, he won the John Player Classic,[8] at that time its £25,000 first prize was the richest offered in golf (in those days, even the British Open champion received just a little over £5,000), it made him that season's leading money-winner, although not Order of Merit leader, which was decided by a points system not directly related to prize money.