CBL-FM was launched in 1946, simulcasting CBL on FM. It originally broadcast at 99.1 MHz, but moved to 94.1 in 1966. (The 99.1 frequency was vacant until 1977, when it was assigned to the CKO radio network. CKO ceased operations in 1989, and the frequency was again vacant until it was assigned to CBLA-FM.)
It began airing separate programming in 1960, along with the other CBC FM stations, in 1960. It became a simulcast of CBL again in 1962, but broke off again in 1964. The FM network was rebranded CBC Stereo on November 3, 1975, and CBC Radio Two in 1997.
On February 15, 1979, the CRTC approved the CBC's application to operate a new FM transmitter in Belleville on 94.3 MHz (CBBB-FM)  and on May 7, 1979, the CRTC also approved the CBC's application to operate a new FM transmitter in Brockville on 104.9 MHz (CBBA-FM), to rebroadcast the programming originating from CBL-FM Toronto. Neither of these transmitters in Belleville and Brockville were implemented  and the frequencies were awarded to other broadcasters.