McClean became Latics’ 10th summer signing of 2013, equalling the record for most signings in a transfer window by the club.
The Republic of Ireland international winger began his career in Northern Ireland where he rose to catch the eye of Sunderland while playing for his local club Derry City.
McClean spent three years at the Candystripes from 2008-2011, scoring 18 league goals in 78 appearances.
He scored on his debut for the club with a goal in the League of Ireland Cup in 2008.
McClean signed for Sunderland when he was snapped up by former Latics manager Steve Bruce in August 2011, however it was the Black Cats’ next manager Martin O’Neill who would hand him his debut in December 2011 against Blackburn Rovers.
The left sided winger scored his first goal in English football against Latics at the DW Stadium in January 2012 and went on to play over 50 times for Sunderland.
He was voted the club’s Young Player of the Year for 2011-12.
On the international stage McClean made his debut against Czech Republic in February 2012 and was part of Republic of Ireland’s squad for the 2012 European Championships.