The star, who was awarded for his services to the entertainment industry and to charity in the Queen's Birthday Honours list earlier this year, said he was 'deeply proud' as HRH presented him with his award.
Both Gary and the Queen beamed as she pinned the OBE on his grey morning suit at the investiture.
It was announced he was to receive the honour just days after he put together the triumphant Diamond Jubilee concert at Buckingham Palace in June.
He also co-wrote charity single 'Sing' with Andrew Lloyd Webber for the celebration, which saw him travel all over the globe to capture 210 voices from across the Commonwealth.
His other charity work has included gathering a team of celebrities to climb Mount Kilimanjaro in 2009 for Comic Relief and organising charity concerts for Children in Need in 2009 and 2011.
Gary declined to speak to reporters at today's event, but did say in a statement that it "hadn't seemed real until today".
Ahead of the event this morning, Gary also tweeted: "I'm going to get my O.B.E. thank you for all your support over the last 21 years."