Gregory has decided to leave Emap after almost 11 years working on its broadcast strategy and, for the past two years, running its national radio brands including Kiss and Magic.
His responsibilities will be taken on by the management teams at Magic, Kiss and Kerrang!, who will now report to Dee Ford, the group managing director of Emap Radio.
During his time at Emap, Gregory helped it develop its digital strategy and helped turn Magic 105.4 into the London market leader.
As the development director of Emap Performance, he worked with Tim Schoonmaker, its then chief executive, on nine digital licence applications and on building Emap's presence on Freeview.
Gregory said: "I set out with a lot of objectives which I've now completed. Media is at an interesting crossroads and I want to be at the centre of all that."
Schoonmaker, who left Emap in 2004, has been linked with a potential bid for GCap Media through the the equity company Permira. He is set to float his Media Acquisition Company on AIM.