KXOA-FM began as a simulcast of KXOA in 1945. During this period, KXOA broadcast a traditional MOR/block programming format. In the mid-1950s, KXOA changed to a Top 40 format. KXOA-FM continued to simulcast the AM station through the 1960s. However, the station briefly ran a Country and Western format as KCNW-FM. The format and call letters ran from the Summer of 1961 through the Summer of 1962, when KRAK (1140) debuted with a Country and Western format. The station returned to simulcasting KXOA and re-adopted the KXOA-FM call letters. In the 1960s, the FCC dictated that all FM stations in areas having a population greater than 250,000 people must dedicate at least 50% of their broadcast schedule to separate programming from AM sister stations. In the late 1960s, KXOA-FM partially separated from its AM counterpart and broadcast adult contemporary music from 7:00 a.m. to 3:00 p.m., and then simulcasting KXOA's Top 40 programming until it signed off at midnight.