During his college years in Chicago, Guercio had become friends with a saxophonist named Walter Parazaider. Parazaider invited Guercio to hear his new band, "The Big Thing", and Guercio offered to manage and produce them. He relocated the band to Los Angeles in 1968, convinced them to change their name to "The Chicago Transit Authority", and arranged for them to appear in local clubs where they quickly became popular. While recording their first album for CBS/Columbia, Guercio was also approached about producing a second album for Blood, Sweat & Tears. Both of these highly successful albums were released in 1969, and "Blood, Sweat & Tears" won Guercio an Album of the Year Grammy Award.