The 50-year-old musician - who joined the 'Supersonic' rockers in 2000 after original guitarist Paul 'Bonehead' Arthurs' quit - is listed as the touring group's rhythm guitarist and backing vocalist on the site with Tim Smith now listed as an ex-member, departing in 2017.
The move could anger Liam Gallagher, who formed Beady Eye with Gem and fellow ex-Oasis members Andy Bell and Chris Sharrock after Noel quit the group in August 2009 following a huge backstage bust-up with his younger brother.
Beady Eye eventually disbanded in October 2014 after releasing two albums, 'Different Gear, Still Speeding' and 'BE'.
As well as playing guitar in Oasis Gem also contributed several songs, including 'Hung in a Bad Place' from 2002 album 'Heathen Chemistry', which was the first track not penned by a Gallagher brother to feature on one of the group's LPs.
Gem last performed with Noel in December 2015 at the Royal Albert Hall in London when he joined him for a special acoustic set of Oasis B-sides and re-worked classics, such as 'Listen Up', 'Sad Song', 'Slide Away' and 'Wonderwall' ahead of Noel's performance with his full band.
That gig was preceded by a show at Bishop Grosseteste University in Lincoln, East Midlands, in front of an intimate audience of just 200 fans.
The Lincoln show marked the first time that Noel and Gem had teamed up since they joined forces for Noel's Teenage Cancer Trust show at London's Royal Albert Hall in March 2010.
Although he quit Oasis, Noel remained friends with Gem and after the demise of Beady Eye he urged his brother Liam, 44, to keep working with the six-string strummer.
The 'You Know We Can't Go Back' songwriter said: ''If I was giving him (Liam) any advice, I think he should stick with Gem as his wingman, because they were great mates and Gem really understood him.''
Liam is currently preparing for the release of his debut solo LP 'As You Were' and has been busy in rehearsals ahead of his tour.
The rock 'n' roll star has also been pinching band members as he has swiped Pete Doherty's bassist Drew McConnell for his shows.
Pete, 38, recently said: ''Stressification on the band front, Drew playing bass guitar for Liam Gallagher's new tour. (sic)''
The pair - who have been at loggerheads for years - have another person in common as they both have children by 90s indie rocker Lisa Moorish.
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