Guardian Media Group has bought Saga Radio giving it ownership of radio franchises currently operating in East Midlands, West Midlands and Glasgow and a fourth due to launch in the North East.
According to GMG, the four services will cover a population of 9.5 million; the current stations reach an audience of 849,000 adults.
GMG – which owns the Guardian and Observer – now owns 12 FM radio stations, including several Century Stations and Smooth FM (formerly Jazz FM).
GMG chief executive Carolyn McCall said: “This further expansion of our radio division will help to ensure the continued success and growth of GMG.
"The addition of these stations to the portfolio gives GMG Radio real scale and confirms its status as a major player in the UK radio market."
GMG claims that the new acquisitions will make it the third largest commercial radio group in terms of total hours broadcast by the end of the year.
The Saga stations are to be re-named in “due course”.