In May 2004, Oseary partnered with Jason Weinberg and Stephanie Simon to become a principal in Untitled Entertainment, a management company with offices in Beverly Hills and New York City. In 2005, Oseary became the manager for his longtime business partner Madonna and guided her through the Confessions Tour (2006), Sticky & Sweet Tour (2008–09), and The MDNA Tour (2012), which are among the highest-grossing concert tours of all time. He won Top Manager at the Billboard Touring Awards in 2006 and 2009. In 2007, Oseary negotiated a 360 deal partnering Madonna with Live Nation worth $120 million. On November 12, 2013, it was announced that Oseary would be replacing Paul McGuinness as manager of U2 in a $30 million deal which would see Live Nation buy both Maverick and U2's management company Principle Management. McGuinness was quoted as saying "I have long regarded Guy Oseary as the best manager of his generation, and there is no one else I would have considered to take over the day-to-day running of our business." Oseary is also the manager for Amy Schumer.