O’Malley started practising law in 1975 at what was then Gray Cary Ames & Frye, and formerly chaired each of that firm’s Corporate, Real Estate and Commercial Law practice groups. From 1987 through to 1991, he served as vice-chairman and executive vice-president of Noble Broadcast Group, one of the US’s largest privately held radio groups, as well as special counsel to Gray Cary.

He returned to Gray Cary in 1992, where his practice involved a broad range of financial and corporate matters in various industries. He was elected chairman and chief executive officer of Gray Cary Ware & Freidenrich in April 1996, developing it into a nationally recognised technology law firm with offices in seven cities from Silicon Valley to Washington, D.C. On 1 January 2005, Gray Cary merged with Piper Rudnick and DLA to form DLA Piper.

O’Malley earned his Bachelor of Arts degree at the University of Notre Dame in May 1972. He graduated from Stanford Law School in January 1975, where he was awarded the Order of the Coif, and was a member of the Stanford Law Review. He has served on a number of corporate and civic boards of directors and is currently on the board of the University of San Diego Real Estate Institute. O’Malley is a frequent speaker on issues relating to law firm management. He is a member of the State Bar of California and the State Bar of Texas.

In 2006, the California Daily Journal named O’Malley to its list of the Top 100 Influentials in the California law community. In 2007, the Daily Journal recognised him as one of the Top 100 Attorneys in California. He has been named a San Diego Super Lawyer.