The Irishman started his career as a trainee at Millwall having previous played for Irish outfit Belvedere. Cogan eventually made 24 Football League appearances for The Lions.|
On 27th February 2004, Cogan made his Republic of Ireland Under-21 debut in the Madeira International Tournament against a Madeira Select XI.
Cogan featured for Millwall in the 2004 FA Cup final against Manchester United, coming on as a substitute in the 74th minute for Robbie Ryan. They lost 3-0.
He also came on as a sub in Millwall's home tie against Hungarian side, Ferencvaros, in their short UEFA Cup campaign. In the 36th minute he came on for Jody Morris who limped off injured.
The right-winger left Millwall in the summer of 2006 and joined Barnet for an undisclosed fee. He spent just one season making 39 League Two appearances scoring three times.
In May 2007, Paul Flairclough released a number of players. These included future Grays goalie Ross Flitney, Magno Viera (currently on loan at Cambridge United from Crawley Town) and Anthony Charles (Aldershot Town).
Ronnie Jepson signed Cogan for Gillingham on 20th June 2007. He made 21 appearances in all competitions scoring just one goal, before the Gills new manager Mark Stimson sent him on loan to Grays Ath alongside former club captain Stuart Thurgood in mid-March 2008.
Details correct as of 16th March 2008.