On May 2, 1960, at 6 a.m., WLS went full-time Rock and Roll/Top 40. Mort Crowley was the first disc jockey under the new format, and the first song played was "Alley-Oop" by the Hollywood Argyles, four full weeks before it debuted on the Hot 100. The station's jingles were sung by the Anita Kerr Singers.
Ralph Beaudin was the station's president and general manager, and oversaw the station's transformation into a rock and roll / top 40 station. Sam Holman was the station's program director and an afternoon DJ. Beaudin and Holman were both brought in from KQV in Pittsburgh, Pennsylvania. Ed Grennan, an announcer on the station since 1959, was retained as a DJ under the new format. Star disc jockey Dick Biondi, a 1998 inductee into the National Radio Hall of Fame, was brought in from WEBR in Buffalo, New York. Biondi remained on the station until 1963. Other DJs who were brought in for the station's new format included Bob Hale from WIRL in Peoria, Illinois, Gene Taylor from WOKY in Milwaukee, Wisconsin, Mort Crowley from WADO in New York City, and Jim Dunbar from WDSU in New Orleans, Louisiana.
In October 1960, Art Roberts joined the station as a DJ, having previously worked at WKBW in Buffalo, New York. Clark Weber joined the station as a DJ, remaining with the station until 1969. In 1963, Ron "Ringo" Riley joined the station as a DJ, having previously worked at WHK in Cleveland, Ohio. Dex Card joined the station in 1964, and hosted the Silver Dollar Survey countdown until 1967, the longest of the show's hosts. In 1967, Larry Lujack joined WLS as a DJ, four months after he had started at the station's top competitor WCFL. Lujack returned to WCFL in 1972, but rejoined WLS in 1976, remaining with the station until 1987. In 1972, John Records Landecker joined WLS, remaining with the station until 1981. Landecker returned to WLS in 1986, and remained with the station until its format was changed in 1989. Tommy Edwards joined the station as production director in 1972, becoming program director one year later, and later becoming a mid-day DJ. Bob Sirott joined WLS in June 1973, remaining with the station until December 1979.
Other DJs on WLS during its top 40 era included Chuck Buell, Kris Erik Stevens, Joel Sebastian, Gary Gears, Jerry Kay, Yvonne Daniels, Brant Miller, Tom Kent, Steve King, Jeff Davis and Fred Winston. Some of the production directors responsible for the sound of WLS were Ray Van Steen, Hal Widsten, Jim Hampton, Bill Price and Tommy Edwards.
In the 1960s, WLS was a major force in introducing new music and recording artists. The first US airplay of a record by The Beatles ("Please Please Me") was on Dick Biondi's show on February 8, 1963.
WLS was voted by broadcasters nationally as "The Station of the Year" in 1967, 1968 and 1969. John Rook was named "Program Director of the Year" in 1968 and 1969 as WLS was estimated attracting 4.2 million listeners weekly by Pulse research.
WLS also produced the weekly Silver Dollar Survey from October 14, 1960, to December 22, 1967, broken by the Silver Beatle Survey on February 21, 1964 (see picture to the right) and the Super Summer Survey from May 5, 1967, to August 25, 1967. The survey nominally contained 40 current listings, except for occasional weeks when it contained less current listings, usually 20, plus a special listing of greatest oldies. From 18 September 1964 through 25 December 1964, the survey consisted of the top 30 pop hits, followed by the top 10 R&B hits. Thereafter, the survey changed its name numerous times (89 WLS Hit Parade, 89 WLS Chicagoland Hit Parade, WLS Musicradio 89, etc.). Starting with the July 20, 1970 survey, the number of listings dropped from 40 to 30, then varying from 25 to 40 starting June 26, 1972, then dropping to 15 by March 9, 1974, then increasing to a high of 45 by the end of 1975. No "take home" surveys were printed from March 13, 1972, through July 16, 1973 (these were limited to one poster-size weekly survey displayed at record shops). The year-end listing was the 20 greatest hits of the year for each year from 1963 through 1966, increased to 89 from 1967 onward.
Like many AM radio stations of the seventies, WLS edited many of the songs they played into a more "radio-friendly" or "radio edit" (a term still used today) format, usually 3–4 minutes in length. Other special editions of some Top 40 songs exclusively made for their broadcasting were done by the musicians themselves or sometimes by the WLS audio engineers. An example of these included Reunion's 1974 song "Life Is a Rock (But the Radio Rolled Me)". Reunion changed the song's lyrics from "Life is a rock but the radio rolled me" to "Life is a rock/WLS rolled me". A similar version was made for competitor WCFL. Another "WLS-only" version was a combination of Captain and Tennille's "Love Will Keep Us Together" and "Por Amor Viviremos", which featured alternating English and Spanish vocals.