Gregory joins Radio UK, which is backed by the Australian investment bank Macquarie, as its chief executive.
His first task is expected to be the management of the company's new radio station in Plymouth, Diamond FM. He will also work with Schoonmaker, Radio UK's chairman and the former chief executive of Emap Performance, on winning more radio licences.
Gregory, who resigned as the managing director of national brands at Emap Radio two months ago, has experience of launching stations for Emap across the country. He also ran brands including Magic, Kerrang! and Kiss.
Macquarie owns 85 radio stations in Australia and has raised £400 million to acquire overseas interests.