The Foo Fighters frontman recorded drums for the new Washington band's upcoming debut album, which is due out later this year.
The band explained that they met Grohl while recording at the Sound City Studios in 2012 and he was shooting for his new documentary film about the legendary studios.
Talking about Grohl's contribution to the record, RDGLDGRN told NME that he "knocked out half our record like some kind of machine".
They added that it was "overwhelming" to work with the star, and hinted at the possibility that Grohl will tour with them later in the year.
Meanwhile, Grohl recently formed an supergroup called the Sound City Players, with members including Stevie Nicks, Nirvana's Krist Novoselic and Pat Smear and Foo Fighters' Taylor Hawkins.