Brennan practices with the Financial Regulatory and Corporate team where he focuses in the areas of banking law and corporate and securities law, with an emphasis on corporate finance-related activities. He provides strategic counseling to a broad range of clients ranging from "inflatable" charter and de novo banks to start-up technology services companies and multibillion-dollar public entities. During the financial crisis of 2008-2009, and the period following the crisis, Brennan represented numerous banks in pursuing distressed banking transactions, including failed bank acquisitions, bankruptcy sales, and recapitalizations. He recently served as Chief Operating Officer of a $20+ billion publicly traded Midwestern Regional Bank, where he supervised risk management, including regulatory relations, credit, compliance, legal, and related corporate development functions, including integration activities and vendor programs. He is a frequent speaker regarding financing and strategic transactions in the financial services area and is often quoted in national and local publications.