Making a radical change in prime-time television, NBC is moving late-night talk show host Jay Leno to 10 p.m.

The move would keep Leno from bolting to a rival network, as he has hinted. It also upturns decades of conventional wisdom that has kept the networks in lock-step in how they fill their prime-time schedules.

For decades, NBC, ABC and CBS have plugged the 10 p.m. hour with cop shows and medical dramas that have become increasingly costly to produce. NBC, which is in fourth place, hopes the gambit will staunch the bleeding in prime time and the loss of ad dollars by instead airing the lower-cost and potentially higher-profit talk show.

Leno is scheduled to sign off as “The Tonight Show” host at the end of May to make room for Conan O’Brien, who would become the fifth host in the show’s 54-year history.

NBC earns about $50 million a year in profit on “The Tonight Show.”

“Jay gets to stay at his home, and NBC gets the benefit of his genius,” said one person close to the situation who asked not to be identified because NBC was trying to keep the move under wraps until Tuesday’s announcement.

NBC Universal Chief Executive Jeff Zucker nearly five years ago engineered “The Tonight Show” hand-off as a way to avoid the decision that NBC experienced 16 years ago when it picked Leno over David Letterman to replace Johnny Carson. Letterman then defected to CBS, initially taking a chunk of “The Tonight Show” audience with him.

Although Leno agreed to go along with NBC’s transition plan, the 58-year-old comedian became increasingly frustrated that NBC was moving him out before he was ready to retire. He frequently made light of his plight during his monologue, and NBC’s struggles in the ratings became a frequent butt of his jokes. ABC and Fox have expressed interest in him for late-night projects.

The deal to keep Leno behind his desk solves another costly dilemma for NBC. Only two of its 10 p.m. dramas have been solid performers, “Law & Order: SVU” on Tuesday night and the longtime Thursday night drama, “ER.” This is “ER’s” final season, and its departure was expected to leave a gaping hole in NBC’s schedule.

Zucker appeared to be paving the way for the Leno announcement Monday when he told an investor conference in New York that NBC was weighing cutting back the amount of its weekly prime-time programming to save money.

“Can we continue to program 22 hours of prime time? … Can we afford to program seven nights a week?,” Zucker said. “All of these questions have to be on the table.”

Now, the network will have to come up with only 17 hours of shows. Such a move by one of the major broadcast networks would have been unthinkable only a couple years ago but is no longer met with surprise as the industry grapples with audiences “time shifting” their viewing and watching shows online.

Zucker’s remarks came as NBC continued laying off employees as part of $500 million in budget cuts and a shake-up of the programming department that forced several top executives from their jobs.

A little over a month ago, Zucker and NBC Entertainment Co-Chairman Marc Graboff offered Leno the Monday-Friday time slot, according to the person familiar with the deal.

His longtime executive producer, Debbie Vickers, will continue to be in charge of the show.

A new soundstage is being prepared a couple of miles away, on the Universal Studios lot, for O’Brien, who takes over “The Tonight Show” in June.

It was unclear late Monday when Leno’s prime-time show would begin or how long his contract would run.

Staff writers Maria Elena Fernandez and Scott Collins contributed to this report.

Broncos runningback Peyton Hillis lies in pain after an injury in the second quarter against the Chiefs at Invesco Field at Mile High in Denver Sunday, Dec. 7, 2008. Photo by (Christian Murdock/The Gazette)