The 50-year-old musician - who joined the 'Supersonic' rockers in 1999 after original guitarist Paul 'Bonehead' Arthurs' quit - is officially the touring group's rhythm guitarist and backing vocalist.
The 'Riverman' songwriter, also 50, shared a picture of his band rehearsing for their shows with U2 for their 'Joshua Tree Tour' this summer.
Ex-Oasis member Chris Sharrock - who joined Oasis in 2008 after previous drummer Zak Starkey left the group - who has been in High Flying Birds since last year is also in the shot.
Hitting back at his brother Liam after he blasted the Irish rockers as a ''bunch of beige f***s, Noel captioned the photo on Instagram: ''We are pretty much ready.
The tunes have been given a good polish.
Everyone has been reacquainted.
We have new members!
We are very much looking forward to seeing old friends and maybe making some new ones but what we are most excited about is sampling the delights of The U2 Catering Experience ... widely regarded as THE MOST superior catering experience anywhere in the music business..see you out front.
AS YOU WEREN'T..KISS-KISS.. NG (sic)''
The move would likely anger Liam, who formed Beady Eye with Gem and fellow ex-Oasis members Chris and Andy Bell after Noel quit the group in August 2009 following a huge backstage bust-up with his younger brother.
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.
Liam, 44, 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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