After leaving Gong, Howlett formed the short-lived band Strontium 90, which consisted of himself, Sting, Stewart Copeland, and Andy Summers. In addition to being the band's lead bassist and chief songwriter, Howlett performed most of the lead vocals at live performances. The band recorded several demos and played at a Paris Gong reunion concert in May 1977, but disbanded when Summers left to join Copeland and Sting's other project, The Police. An archival collection of Strontium 90 material was released two decades later as Strontium 90: Police Academy.
A few months after the breakup of Strontium 90, Howlett served as bassist for the one-off studio band The Radio Actors, which also included Gong bandmate Steve Hillage on lead guitar and Strontium 90 bandmate Sting (who came to the group by way of Howlett's recommendation) on lead vocals. The band's single, "Nuclear Waste" b/w "Digital Love", was reissued on CD in 1995 with liner notes and three bonus tracks, though none of the bonus tracks involved Howlett.
Gong performs occasional reunion gigs around the world, and Howlett usually joins them. In 1993 he launched a record label, Mauve, which released albums by singer-songwriters Rafa Russo, Debbie Cassell and Jay Fisher. From 2005 to 2009 Howlett was chairman of the Music Producers Guild (MPG).