Mr Cowley has been in the seat for six years, and worked with three MinterEllison CEO's – John Weber, Tony Harrington, and now Annette Kimmitt.
"Bruce has been critical to the success of MinterEllison, and has guided us to where we are today," said Mr O'Brien. "Under Bruce's leadership, we are now the largest law firm in Australia."
Mr Cowley has been with the firm since 1981 and a Partner since 1987. He has held a number of leadership positions in the firm, and has acted as Chair of the Firm for the past six years.
During Mr Cowley's time as Chair of MinterEllison, the firm was the first in the market to move into adjacent non-legal consulting businesses.
"MinterEllison is poised for an extremely exciting future," said Mr Cowley. "We now have well over 250 talented Partners, and an exceptional new CEO in Annette Kimmitt who will take the firm to new heights."
Mr O'Brien is a long-standing Partner of the firm, and is based in its Brisbane office. He specialises in corporate and financial litigation and reconstruction law.
"David is our longest serving Board member, and is focused on ensuring the Board and management team continues to drive this momentum under his leadership," said Mr Cowley. "The firm is lucky to have David step in and continue to build on the great success that the firm has had over the past six years."