played forward for the North Carolina Tar Heels women's soccer program from 2003 through 2006. She appeared 97 times for the Tar Heels, scoring 59 goals and assisting on 49 others. She led her team to the national Championships in 2003 and 2006. During her senior year, ESPN the Magazine named her the All-American Player of the Year and was awarded the NCAA's Today's Top VIII Award following her senior year. As a senior, she won the Honda Sports Award as the nation's top soccer player. In 2006, O'Reilly's No. 20 jersey was retired by the program, joining athletes April Heinrichs, Lorrie Fair, Tisha Venturini, Kristine Lilly and Mia Hamm, along with 13 others. Club career New Jersey Wildcats, 2004–2005 O'Reilly played for New Jersey Wildcats of W-League from 2004 to 2005, winning the Championship in 2005. Sky Blue FC, 2009–2011 O'Reilly was allocated to Sky Blue FC of Women's Professional Soccer on September 16, 2008, along with fellow U.S. national team players Natasha Kai and Christie Rampone. She appeared in 17 matches as co-captain during the 2009 inaugural season, leading Sky Blue to an unexpected playoff berth. During the Championship 2009 Women's Professional Soccer Playoffs match against Los Angeles, she scored the only goal helping her team clinch the Championship title. Boston Breakers, 2012–2014 Following her husband's enrollment in Harvard Business School, O'Reilly trained with and played two matches with the Boston Breakers of the Women's Premier Soccer League Elite in 2012 after the WPS folded and during breaks with her national team duties. She was allocated to the Breakers in 2013 at the initiation of the new National Women's Soccer League. FC Kansas City, 2015–2016 On October 27, 2014, FC Kansas City announced that it had acquired O'Reilly in a trade that sent Morgan Marlborough and Kassey Kallman to the Breakers. Arsenal, 2017–2018 On January 18, 2017, Arsenal announced they had signed O'Reilly. The club is a member of the top division of the Football Association Women's Super League, the highest level of women's professional soccer in England. After 38 appearances in all competitions and four goals, it was confirmed by Arsenal that she would leave the club in the summer of 2018. North Carolina Courage, 2018–2019 After FC Kansas City ceased operations, the Utah Royals FC maintained O'Reilly's NWSL rights. On June 28, 2018, the Courage traded Makenzy Doniak and a 2019 3rd round pick for O'Reilly