He graduated from University College, Dublin, as a veterinary surgeon in 1973, and worked as his father's assistant before taking over the stable in 1979.
In 1995 he trained Ridgewood Pearl, bred and owned by Sean and Anne Coughlan, to victories in the Irish 1,000 Guineas, the Coronation Stakes at Royal Ascot, the Prix du Moulin at Longchamp, and the Breeders' Cup Mile at Belmont Park, in America, meaning that the filly had six wins from eight races and that she had won Group One races in four different countries in the same season.
[7] When he decided to withdraw his racehorses from England following Aliysa's disqualification in The Oaks of 1989,[9] he established a significant presence in Oxx's yard.
[10] Without a budget of his own to spend on yearlings, Oxx continued to be reliant on horses bred by owners with whom he had an association.
[4][11] In 2000 Oxx trained the Aga Khan's brilliant Sinndar to wins in the Epsom Derby, the Irish Derby, and the Prix de l'Arc de Triomphe, making the colt the only horse ever to have won that trio of races and at that time one of only three Irish-based horses that had ever won the Arc.
[6][14][15][16][17] Oxx was typically understated when assessing the role of the trainer in the career of a great horse like Sea The Stars.