Bowie is an interesting case. For the most part, I don’t think he really fits, though his work was often informed by what was going on underground. There are, in my view, four or five Bowie LPs that should be in the prog rock conversation on one level or another: Space Oddity, The Man Who Sold the World, Station to Station, Low, Heroes, and maybe Lodger. “Cygnet Committee” was a late cut from my 1969 volume.
All of those albums have songs that certainly contain elements associated with progressive rock, and I think that, as a pop star and innovator of glam rock, he’s a good reminder of just how thoroughly ideas injected into rock by prog artists permeated the music in the 1970s. Also, a look at the credits for his albums reveals that he often worked with the guys who were making that music. Rick Wakeman plays on Space Oddity and Hunky Dory, for instance, and of course he worked with Fripp and Eno, Terry Cox (Pentangle/Nucleus), Tim Renwick (session guy with tons of prog credits, later toured with Pink Floyd), Trevor Bolder (Uriah Heep), Aynsley Dunbar, Herbie Flowers (Sky), Ricky Gardiner (Beggar’s Opera), Adrian Belew, Simon House (Hawkwind), and others. It could be argued that Bowie is among the surprisingly common bridges between prog and punk.
Mostly, though, I think Bowie kind of inhabits his own weird little space as a challenging pop artist willing to compromise his commercial momentum by experimenting. He was, after all, foremost a stylist, and when he dips into prog, he sounds a bit like he’s visiting it from another planet. That said, he will be on an upcoming volume, though I’m going to be coy about which one (there are five remaining volumes).