John O'Neill played in nine grand finals, winning premierships with Souths before transforming Manly from bridesmaids to champions. O'Neill, a tough, rugged prop forward from Gunnedah, joined the Rabbitohs to become part of a famous forward pack that also included John Sattler, Elwyn Walters, Ron Coote and Bob McCarthy. He became renowned for his barging runs and brick-wall defence. He was known as arguably the toughest, most uncompromising player of his era - a bloke who gave as good as he got.

Born in Griffith but reared in the northern town of Gunnedah, in his early twenties, John O'Neill showed plenty of promise in appearances for Country against both City and the French tourists and was spotted by Sydney premiership talent scouts. He lived in the town, and did an apprenticeship as a carpenter. In 1964, after watching him play in the second row for Country Seconds and for NSW Colts against France, South Sydney snapped him up him for £1000. What a cut-rate transfer fee it turned out to be. O’Neill's partner in the second row in that Colts’ game, incidentally, was a young man called Bobby McCarthy.

O'Neill came to South Sydney in 1965 and his aggressive play in the scrums and charging runs close to the rucks caused him to be noticed. His toughness and solidity earned him the nickname "Lurch", and in his debut season O'Neill played for South Sydney in the Grand final against the champion St George team. A tall and strongly framed man, O'Neill was able to develop consistently as he built up his weight from 88 kilograms in 1965 to 104 kilograms by 1970. Between 1967 and 1971 he played in five grand finals for South Sydney, winning all but the 1969 contest against Balmain.

In the famous 1970 grand final, O'Neill was even more punishing after Sattler suffered a fractured jaw and his performance that day ensured his selection in the 1970 World Cup squad. In the final of that tournament, O'Neill dished out plenty of punishment in the first half, and was the target for retribution in the second. Afterwards, he was battered, his shin split to the bone, but all he could talk about was how Billy Smith had played on with a badly gashed leg.

O'Neill was a force in Manly's initial first-grade grand final win, a 19–14 victory over Easts in 1972, and staged a running battle with his opposite number, Englishman Cliff Watson, when the Sea Eagles beat Cronulla 10–7 a year later.

Financial problems at South Sydney caused him along with teammate Ray Branighan to leave for Manly. There O'Neill played in two more premiership sides, and his battle with Cronulla strongman Cliff Watson in the brutal 1973 grand final (won by Manly 10–7) is regarded as one of the toughest conflicts seen in the Australian game. The 1973 grand final between Manly and Cronulla was certainly no place for the feint-hearted and O’Neill was in his element as he displayed extreme courage and no concern for his body.

O'Neill first played for New South Wales in 1967, and made his international debut in the 1970 World Cup. It was in this match that his remarkable strength in the toughest conflicts first showed itself. He continued to hit opponents in a way that would have been remarkable for anyone with a split shin, and refused to take first aid even when blood spilt into his sock! John O'Neill remained a regular international player until he retired.

In 1975 and still a major force in representative rugby league, O'Neill returned to South Sydney. Paradoxically, though he was superb in representative games, he was disappointing in club rugby league and retired during the 1976 season. O'Neill coached South Sydney in 1977 but could win only one of the last eighteen games and he stood down. During his playing days, O'Neill had developed a highly profitable building business with his Rabbitoh teammate Gary Stevens, which by 1977 would prevent him from devoting his attention fully to coaching. In the 1980s, he used the profits from this business to build a home