It marks the first of a week's worth of charity gigs taking place at the venue on the Kingsland Road in Dalston, East London, with Norman Cook, Man Like Me and Kissy Sell Out performing.
It seems Cook is a regular now at Oxjam events: "This is my third I believe," he said to one of my colleagues at 6 Music (Matt Everitt). "In terms of interesting venues it's a highlight of the year. Me and Zoe [Ball] have got an affinity with Oxfam and a relationship that when they call, we tend to come."
Other acts on the bill throughout the week include Brett Anderson, Patrick Wolf and Ghostpoet tonight (27 September) and Charlie Simpson and Benjamin Francis Leftwich on Wednesday (28 September).
Organisers will also be staging the album launch party on Thursday (29 September) for Damon Albarn's new DRC Music album project, with DJ sets from Totally Enormous Extinct Dinosaurs, Richard Russell, Kwes and James Yuill.
Cook also revealed to 6 Music News that charity shops have had a big affect on his musical career: "I dressed from Oxfam and charity shops when I was young but mainly it was trawling for records.
"I'd say probably about half the samples in my records probably came from charity shops, so I've spent many an hour getting that particular grime you get flicking through dusty old crates in charity shops."
His set at the Oxjam launch marked the end of the summer season, as he explained: "I don't really tour, I just tend to play weekends so it's not really a tour but this is our last show of the official summer.
"We did the Ibiza closing parties last night but for us this is the real deal. This is our end of term party, the 65th show of the year I think. It's been a long season. The summer season begins in Brazil in February."
Since 2006, Oxjam music events have raised £1.5 million to help people around the world.
(I wrote this story for BBC 6 Music News here.)