On October 9, 1956, the station first signed on as KGLA. Noted radio programmer Gordon McLendon bought KGLA in the 1960s, changing the call letters in November 1966 to KADS. McLendon, with permission from the Federal Communications Commission, experimented with an all-advertisement format, hence the call sign choice. One of its features was that listeners could purchase their own commercials on KADS, not unlikeclassified advertising in a newspaper. FM radios were still not widely owned in the 1960s and the experimental format was not successful.
Beautiful music
In March 1968, the station adopted the KOST-FM call sign, along with a substantially all-music format, which was unusual if not unique given then-prevailing license obligations to broadcast at least some news. The station aired a mostly-instrumental beautiful music sound. In 1973, Cox Communications purchased KOST to pair with its newly-bought KFI. KOST, with its call sign pronounced "coast" in a stage whisper, continued its easy listening sound through the 1970s. This popular format was also heard on rivals KJOI and KBIG. In the early 1980s, KOST gradually added more vocals, and on November 15, 1982, the station switched to a soft adult contemporary format. Former Sacramento radio personality Bryan Simmons was KOST's first host when the station signed on with its new format. On February 3, 1986, Mark Wallengren and Kim Amidon made their debut as KOST's new morning hosts. The Mark & Kim Morning Show was one of the longest running shows on Los Angeles radio, airing for more than 20 years until ending in 2007.
AMFM/Clear Channel/iHeartMedia era
In September 1999, Cox Communications swapped KOST and sister station KFI with AMFM, Inc. for 14 stations in several East Coast markets. AMFM was then purchased by Clear Channel Communications in 2000. Over the years, the station has garnered solid ratings. Christmas music is aired from early November through Xmas Day since 2001. KOST experienced little turnover among the air staff until the 2000s. On November 29, 2007, morning show co-host Kim Amidon departed the station. This was followed by KOST's original midday host Mike Sakellarides and longtime traffic reporter Mike Nolan. In October 2008, former KYXYSan Diego radio personality Kristin Cruz joined Mark Wallengren as co-host of KOST's morning show. Cruz left the station in May 2014. In 2009, the midday shift was voice-tracked by former WLTWNew York City personality Karen Carson. In February 2011, Carson resigned to join CBS Radio-owned WWFS in New York. Both Christine Martindale and Ted Ziegenbusch filled in on the midday show until August 2011, when former KBIG midday host Kari Steele took over. Steele now hosts KOST's public affairs programThe Sunday Journal broadcasting every Sunday following Animal Radio, providing interviews with community organizations. Also in August, longtime KOST afternoon personality Bryan Simmons left KOST. Simmons had been on the station since 1982, except between 2002 and 2004 when he hosted the Boogie Nights show at KBIG. In December 2012, Christine Martindale was among the radio personalities laid off from Clear Channel stations. On January 17, 2013, it was announced that Martindale would join KKGO ; her first day at Go Country 105 was February 4. Ellen K, a former co-host on the KIIS-FM morning show and On Air with Ryan Seacrest, took over the KOST morning show on October 19, 2015. Mark Wallengren, who had been part of the KOST morning show since 1986, switched to afternoons, replacing Bruce Scott who joined the station since 2012. Recently, following a trend of most AC's, the coast moved to an upbeat format. The station phased out its soft rock moving artists such as Neil Diamond, Barry Manilow and Air Supply to its HD2 stream. Longtime DJs Mark Wallengren and Ted Zigenbusch departed the station on January 16, 2020 as a result of mass layoffs nationwide by parent company iHeartMedia; the two had been at KOST since the 1980s.
Current and former airstaff
The following is a list of known airstaff with current airstaff positions with parentheses
Jhani Kaye
Mark Wallengren
Kim Amidon
Ellen K
Mike Sakellarides
Bryan Simmons
Kari Steele
Mike Nolan
Bruce Wayne
Mark Denis
Sharon Dale
Chris Roberts
Liz Kiley
Karen Carson
Karen Sharp
Kristin Cruz
Ken Davis
Laurie Sanders
Jan Marie
Ted Ziegenbusch
Lance Ballance
Tommy Jaxson
M.G. Kelly
David K. Jones
Jim Rondeau
Christine Martindale
Shaun Valentine
Cathi Parrish
Jacque Gonzales
Bruce Scott
Tom Parker
Carolyn Gracie
HD programming
KOST broadcasts three digital subchannels:
KOST-HD1 is a digital version of KOST's analog signal.