McGrath represented his native Ireland in the Sydney Olympics in 2000 and was a six-time Irish National Champion in the hammer throw, earning a top 50 IAAF world ranking (2004) and a USATF second place finish (2003) in the event. He also participated in the 1999 World Track and Field Championships and the 1998 European Championships. A three-time Division I All-American, McGrath was a threat in both the hammer and 35-pound weight events, earning All-East recognition eight times, four in each category.
McGrath first served on the Manhattan staff as a volunteer assistant coach from 1995-99, before joining Iona as an assistant coach for six years. He served as head track and field coach at Briarcliff High School from 2010-2017, while also working as a physical education teacher in the Bronx. In 2016, McGrath coached U.S. team member Rudy Winkler in the hammer throw at the Rio Olympics.
With experience at the international, collegiate and high school levels, McGrath has mentored NCAA, Senior National, Junior, and Youth champions. Ten of his athletes have won high school national titles, and four have claimed New York State championships. McGrath also coached Track and Field News' 2013 High School Boys Athlete of the Year. In 2019, three of his Manhattan throwers qualified for the NCAA Outdoor Track and Field East Regionals.
McGrath was inducted into the Manhattan College Hall of Fame in 2008.