But it didn't last and was pretty much over by 1970.
What bands which had been psychedelic, were the earliest to fully abandon the style?
Traffic: Traffic (released October 1968, recorded January - May 1968)
The Byrds - Sweetheart of the Rodeo (released August 1968; recorded March of 1968).
It happened partly by necessity, but there's no doubt that psychedelia was absent on this album. Muddying the waters on The Byrds, though, is that they dipped their toes back into psychedelia with the follow-up, recorded in October of 1968 (Dr. Byrds/Mr. Hyde).
Rolling Stones: Beggar's Banquet (released December of 1968; recorded March-June of 1968).
Anybody earlier than this?