The Free Radio and Gem stations provide local programming to listeners in Birmingham, Wolverhampton, Coventry, Derby, Leicester, Hereford and Worcester and Nottingham.
The independent group arrived on the scene when a consortium led by the former Chrysalis Radio chief Phil Riley bought the stations in 2009. The deal was backed by LDC, the private equity arm of Lloyds Banking Group.
Orion Media’s national ad sales contract is already handled by Bauer Media. The group moved its contract into Bauer in July 2014, ending a five-year relationship with Global Radio’s national team in Leicester Square.
Paul Keenan, the chief executive of Bauer Media, said: "Free Radio and Gem are influential radio stations in one of the UK’s fastest growing regions.
"Bauer’s desire to build out its extensive radio business is testament to the nature of the industry which continues to be a strong, robust and growing platform, thriving in the always-on, mobile, connected world."
The addition of Orion Media brings Bauer Media’s share of the commercial radio industry up to 34 per cent. In recent years Bauer has pursued an aggressive growth strategy, buying Absolute Radio and Planet Rock in 2013.
Adrian Serle, the chief executive of Orion Media, said: "Orion has established market-leading status for audiences and revenues in each of its markets, something our teams should be immensely proud of – we are extremely confident that the business will continue to thrive under Bauer's ownership."
Bauer Media missed out on the chance to buy the stations back in 2008 when Global Radio instead agreed on Riley’s bid. Global needed to sell the stations to avoid a full competition probe into its £375 million acquisition of GCap.
Over the last eight years the commercial radio business has become increasingly consolidated into the two main players, Bauer Media and Global Radio. Global Radio bought the owner of Smooth Radio, GMG Radio, in 2012.