A successor has not yet been named. In the interim period, Reilly's senior executives will report to Peter Rice, chairman and CEO of Fox Networks Group.

Fox Broadcasting is moving in a new direction.

The network's entertainment chairman, Kevin Reilly, who has been at Fox since 2007, will depart at the end of June. The news comes at a particularly challenged time for the network, which rounded out the season flat in the key 18-49 demographic despite airing the Super Bowl -- and again lost the demo crown that the net had handily won for nearly a decade. Outside of genre play Sleepy Hollow, Fox failed to add any new bona fide hits this past year, relying instead on critically beloved niche comedies (The Mindy Project, Brooklyn Nine-Nine), shrinking dramas (Glee, The Following) and an aging reality franchise (American Idol).

A successor has not yet been named. In the interim period, Reilly's senior executives will report to Peter Rice, chairman and CEO of Fox Networks Group.

"21st Century Fox is a great company that has provided me with choice seats at the head table of pop culture over two very rewarding stints both at FBC and FX, and I am grateful to have benefited from the leadership of Peter Rice, Chase Carey and Rupert Murdoch," Reilly said in a statement Thursday. "Peter and I have been discussing this transition for a while, and now with a robust new slate of programming for next season and strength in the FBC ranks, it felt like the timing was as right as it could be. I couldn't be more thankful to my team -- a group of creative, tireless and fun people whose fellowship I will miss."

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The move comes as Reilly was looking to reimagine an antiquated pilot-season model that he believed was putting broadcast at a disadvantage. His campaign to do away with pilot season began with a speech of sorts at the Television Critics Association winter press tour in January. "The broadcast development system was built in a different era and is highly inefficient. It is nothing short of a miracle talent can still produce anything of quality in that environment," he said at the time. He has spent the months since focused on straight-to-series development, shorter seasons and a 52-week schedule.

"Kevin's undeniable creative gift and passion for talent have left an indelible mark on our company, and we're extremely grateful to him for his leadership, beginning with The Shield and Nip/Tuck at FX and continuing through Glee, New Girl, The Following, Sleepy Hollow and Brooklyn Nine-Nine at Fox," Rice said in a statement. "Kevin and I have been discussing his desire for a new challenge for some time, so while everyone at the network will miss his enthusiasm for adventurous television, we all respect his decision and agreed that after the upfront presentation was the right time. I'm personally extremely grateful to Kevin for his partnership during the past five years and look forward to working with him again in the future."

Rumors of management changes at Fox swirled heavily during the upfronts, when a handful of Reilly's comedies didn't appear on the schedule as many expected. Multiple sources suggested it was boss Rice who nixed Reilly's crop, with Rice noting that he had little interest in adding more niche offerings to the mix. Others suggest that Reilly, a favorite among TV reporters for his candor, had grown detached from the creative process, rarely sitting in on pitches and often weighing in late in the development cycle.

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Until recently, Reilly's seven-year tenure at Fox had been marked by critical and commercial success, with a portfolio that included one-time juggernauts 24, House, Bones, Glee and Idol. For nearly his entire run, the latter was key in ensuring that the network would round out the season at No. 1 in the all-important 18-49 demo. (Idol dropped double-digits in the ratings this season.)

In a case of history repeating itself, Reilly leaves Fox with roughly 2½ years left on his contract, just as he did when he was let go at NBC in 2007. (Reilly was replaced by Ben Silverman.) Before NBC, Reilly was a key player at FX, and many suggest he would be a good fit at a cable or digital player, given his taste, experience and interest with regard to where the industry is heading.

Reilly's memo to staff follows:

To my friends and colleagues:

I have decided to resign as Chairman of Entertainment at FBC, effective at the end of June.

While difficult decisions have to be made every day, none have weighed more heavily on me than this. The inspired Fox leadership, coupled with your commitment to excellence at FBC, has provided one of the most rewarding chapters in my life.

I love TV. Always have. Since my mother told me to stop sitting so close and watching so much.

I couldn't feel more fortunate to be afforded the opportunity to preside over a dynamic business, collaborate with the most creative people on the planet and drive culture. And also to be positioned at the nexus of change. It's a fascinating moment in time as the digital evolution brings about radical shifts in consumer behavior. And through it all, the art form of TV has never been stronger or the marketplace more robust.

As invigorating as all that is to be a part of, we all know the daily feeding of the network beast and early morning ritual of waking to an overnight report card does breed a certain type of mania. My first boss, Brandon Tartikoff, described presiding over a broadcast network as "the worst best job in the world." I remember coming up in the business and seeing how the grind turned some executives into grizzled cynics. And I vowed to never become that guy. I have always believed it's incumbent upon network brass to bring a wide-eyed optimism to the chairs they rent. Talent deserves that. And frankly, the jobs are just no fun otherwise. Staying fresh and looking forward is part of why I feel the timing is right for me to turn the page now.

As you, my colleagues, know all too well, I am rarely satisfied. But I hope you all also know that I am very proud of what we have accomplished together and of the exceptional entertainment we have helped bring to fruition. We put shows and songs at the top of the charts, we took home trophies, we got out ahead of defining and building and measuring the multiplatform universe and we rewrote rules about how to develop, program and market TV. And I think some of the best is yet to come next season. It's been a satisfying blast.

Thanks for all,

Kevin

P.S. – Don't go back to pilot season!