A chance encounter with a group member led Douglas to help engineer The Who's early (aborted) sessions for Who's Next at The Record Plant. After this landmark recording he was given a chance to engineer John Lennon's classic Imagine album. Douglas and Lennon formed a close bond and worked together for the remainder of Lennon's life.
As a Record Plant staff engineer, Douglas also forged working relationships with Patti Smith, Blue Öyster Cult, the New York Dolls, Cheap Trick, Starz and most notably Aerosmith. Douglas engineered and produced many of Aerosmith's albums in the 1970s, including Get Your Wings (1974), Toys in the Attic (1975), Rocks (1976) and Draw the Line (1977), all of which have gone multi-platinum. Toys in the Attic and Rocks broke Aerosmith into the mainstream and have become highly influential, with both albums ranking among Rolling Stone's list of the "500 Greatest Albums of All Time". His close relationship with Aerosmith extended beyond producing and engineering, as Douglas was also a musical contributor to the group when they came up short of material on their projects. For example, Douglas helped write the band's 1978 hit "Kings and Queens". He was often given the nickname of "the sixth member" of Aerosmith, due to his close relationship with the band. Douglas was replaced as producer by the band for the 1979 release Night in the Ruts, but Douglas was to again work with the group on 1982's Rock in a Hard Place and several of Aerosmith guitarist Joe Perry's solo albums. For much of the late 1980s, 1990s, and early 2000s, Aerosmith worked with other producers, but in the mid-2000s, they re-united with Jack Douglas on the 2004 blues cover album, Honkin' on Bobo. Douglas also produced the band's album Music from Another Dimension!, in 2012. The band continues to maintain a cordial friendship with Douglas.
In the mid-seventies, Jackie Fox, bass player for The Runaways got Douglas to agree to produce their next record but the other band members decided on a different producer (this contributed to the amount of tension between the girls and led Jackie to quit a few months later). 1978 saw Douglas work with the Australian group Skyhooks as executive producer on their Guilty Until Proven Insane album (which included the track "Women in Uniform" which was later covered by Iron Maiden).
In 1980 Douglas was working as producer with Lennon and Yoko Ono on their penultimate Double Fantasy album (for which he won a Grammy Award for Album of the Year). During the same sessions he worked on another Lennon/Ono album Milk and Honey that was to be released later, but Lennon's murder cut that project short (an unfinished version of the album was released in 1984). Douglas was later involved in litigation with Ono over unpaid royalties from Double Fantasy.
Since then he has kept working as an engineer and producer, reuniting with Aerosmith for three more albums and producing albums for artists such as Supertramp, Zebra, Clutch, Local H, Slash's Snakepit and in 2006 the return of the New York Dolls. He is currently working with the Michael Monroe band on their forthcoming album. He has recently finished production with sleaze rock band Blackrain on their new album "It Begins" .