Treacy then repeated this feat in the 1975 IAAF World Cross Country Championships and in the process helping Ireland to the Silver medal in the Junior Team competition.

[7] In the 1984 Los Angeles Olympics, he placed ninth in the 10,000-metre final before crowning his athletics career with a silver medal in the men's marathon.

Winner Carlos Lopes of Portugal was largely unchallenged for much of the race, with Treacy down the field until entering the top six around the 20-kilometre mark.

Treacy continued to work his way up the rankings until entering the Los Angeles Coliseum stadium just behind second-placed British athlete Charlie Spedding.

[9] In the 1985 IAAF World Cross Country Championships, Treacy finished fifth behind Carlos Lopes who had beaten him in the Olympic Marathon of the previous year.

Treacy ran competitively until 1995, retiring following a road race held in his honour in Waterford, attended by the other two medalists from the 1984 Olympic marathon, Carlos Lopes and Charlie Spedding.