In Canada, the band is remembered for several hits, including "California Jam" (1974), "Calling Occupants of Interplanetary Craft" (1977) and "Knee Deep In Love" (1980). In the U.S. "Calling Occupants" b/w "Sub-Rosa Subway" was a minor double-sided hit and their only chart entry, peaking at No. 62 in 1977.
Klaatu's combination of pop, progressive rock, art/symphonic rock, and other genres has often been compared to the Beatles, and sometimes to the guitar-rock of Queen, and the electronic music of Wendy Carlos. British music magazine Shindig! praised the band's ability to combine up-beat pop music with complex progressive rock, forming an "otherworldly brand of progressive pop".
The band, initially a studio-only duo of Woloschuk and Long, released the singles "Hanus of Uranus/Sub-Rosa Subway" and "Dr. Marvello/For You Girl" on GRT Records in 1973, before being taken under the wing of Daffodil Records and its president Frank Davies. With Terry Draper added to the line-up, the singles "California Jam" and "True Life Hero" followed. These early singles credited Dee Long as a writer of several tunes; the others (including "Sub-Rosa Subway", "Dr. Marvello" and the hit single "California Jam") were credited to "Chip Dale," a collective pseudonym for Woloschuk and frequent co-writer Dino Tome. "California Jam" hit the Canadian Top 40, peaking at No. 36, and Klaatu, though they played no live dates, promoted their music by making a television appearance in Canada on the Keith Hampshire-hosted show Music Machine. By 1975, Davies, along with producer Terry Brown, landed the band a deal with Capitol Records in the United States.
Their first album, 3:47 EST (named Klaatu in the US as Capitol Records' executives found the original title too obscure), was released in September 1976, in North America. The band elected to include no photos, no individual musician credits, and no biographical information in the album package; all songs were simply listed as being written and published by "Klaatu." (Note that this collective writing credit covered songs earlier credited solely to Long or to the team of Woloschuk and Tome — even though Tome was not actually a member of Klaatu.) The album was met with moderately positive reviews but by Christmas of that year, sales had stalled.