Noel Gallagher -- I Wrote My Best Lyrics When I Was High!

Listen up Oasis fans -- today is gonna be the day Noel Gallagher throws it back to you ... about how he came up with all those lyrics that have been stuck in your head for years.

The mellower Gallagher brother flew into LA for a show Wednesday, when our photog/Oasis fanboy tried to get answers to every burning Oasis question -- and kinda succeeds.

It's all here in this clip ... "Wonderwall," being bigger than God and the Beatles ... and writing while he was getting high (intentional “Champagne Supernova” plug).

Also covered ... a possible reunion with Liam!! But we all know the answer to that one.