Taylor, who has been with the company since 1996, will take on a part-time consultancy role as non-executive chairman of Livetime, the division of GWR that focuses on delivering digital radio to mobile devices.
GWR will not seek a replacement, with Taylor's chief executive responsibilities to be assumed by Steve Orchard, managing director of local radio, and Roger Lewis, managing director of Classic FM. They report to executive chairman Ralph Bernard.
Shares in the company fell by almost 3% on the news, down by 6p to 210.5p mid morning.
Also set to leave the board at the end of next month is new media and digital director Simon Ward, who will continue to work for GWR on digital radio.
GWR has been selling its overseas radio business to focus on its core UK interests. The company said that now this programme had been completed, it no longer required six executive directors. Taylor and Ward will leave the board after GWR's annual general meeting on July 31.
The group has been disposing of its assets overseas and in the UK, selling its 49% stake in London News Radio to Chrysalis and its interest in DMG Radio Australia to the Daily Mail & General Trust. The company has reduced its debt by around £100m to £66m in the process.
Taylor said: "We have positioned our business in the UK as a more focused company with a strong management team, and it is entirely appropriate that I now move on.
"GWR has great opportunities for creating value for shareholders through the uptake of digital radio. I am delighted to have the opportunity to continue my association with the group through the Livetime project."
Taylor joined the board of GWR as finance director and deputy chief executive, before being promoted to the role of chief executive two years ago.
Bernard said: "In his seven years as finance director and chief executive, Patrick has shown total commitment to maximising the value of GWR's business and has achieved much. The board wishes to place on record its deep gratitude to Patrick and also to Simon for their contributions to the board.
"We are pleased that we shall continue to have the benefit of their knowledge and experience in their new roles at Livetime and in the digital division, where there is so much potential value to be added."
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