After living in Sweden for a period of time, Bundrick united with Nash in London, where he wrote several songs for and played on Nash's hit 1972 album I Can See Clearly Now, which spawned a massive hit single with its carefree title track. Through Nash, Bundrick met Bob Marley, and lent his synthesizer/keyboard talents to Marley's 1973 release Catch a Fire. Around the same time, Bundrick was asked to join an offshoot project of the British blues-rock outfit Free called Kossoff, Kirke, Tetsu & Rabbit, who spawned a lone self-titled release before splitting up. But it was through these projects that the floodgates for further session work seemed to open for Bundrick, as he played on recordings by Sandy Denny, Andy Fairweather-Low, Jim Capaldi, Eric Burdon, Donovan, John Martyn, Silverhead, and Free (the latter of which briefly reunited after the dissolution of Kossoff, Kirke, Tetsu & Rabbit).

The early '70s also saw Bundrick issue his first few solo releases, 1973's Broken Arrows and 1974's Dark Saloon, but session work was his main focus, as he developed a friendship with Who guitarist/songwriter Pete Townshend while playing on his 1977 collaboration with Ronnie Lane, Rough Mix. Bundrick then accepted an invite to join British hard rockers Crawler, but besides a pair of albums (1977's Crawler and 1978's Snake Rattle & Roll), Bundrick's stint with the group proved unfruitful. It didn't take long for Bundrick to latch onto his next project as the Who were looking to add a keyboardist to their touring lineup for their comeback 1979 world tour. Bundrick got the gig (with his first rehearsals with the group documented on the Who's fine home video/DVD Thirty Years of Maximum R&B Live), and has remained as the group's touring keyboardist ever since, in addition to playing on subsequent solo releases by Who members Townshend (1980's Empty Glass, 1985's White City: A Novel, 1989's Iron Man: A Musical) and Roger Daltrey (1980's McVicar, 1994's Celebration: The Music of the Who).

Bundrick has also found time to issue countless further solo releases on his own, including such titles as Abendstimmung: Evening Bliss, Dreamcatcher: Global Journey, Dream Jungle, Echoes of Africa, The Fairy Garden, Moccasin Warrior, Moccasin Warrior II, Run for Cover, Same Old Story, Spirit of the Wolf, Tour Guide, Welcome to America, and With the Dolphins. Additionally, Bundrick has kept up his steady session work schedule, guesting on latter-day releases by such artists as Mick Jagger, Roger Waters, Mick Taylor, Richard & Linda Thompson, and Trevor Rabin, among others.