[2] Upon graduating from McGill, O'Neill spent 10 years with a Canadian business magazine and managed Wallace Publishing Company.

[3] In 1966, O'Neill was selected by Clarence Campbell to be his assistant manager with the eventual goal of succeeding him as president of the National Hockey League (NHL).

O'Neill organized the schedule in a way that allowed 444 games to be played in arenas within a span of 25 weeks in 12 cities as far as 2,704 miles apart.

[2] Beyond the draft, O'Neill used his position as executive director to promote a reduction in violent play on the ice, which he deemed "hooliganism".

[6] After Campbell retired in 1977, O'Neill was named the NHL's executive vice-president and took over all player disciplinary cases.

[7] During his first few months in the position, he advocated for harsher penalties for dangerous plays on the ice which result in injury.