O'Shea started in entertainment at an early age[clarification needed] playing traditional Irish music, touring Europe with several groups. While at college he studied theatre and went on to star in several theatrical productions. He also worked in the National Theatre of Ireland, the Abbey Theatre. He won the Harp Newcomer Comedy Award in 2000 and performed in the BBC Newcomer Awards the same year. He was chosen to perform in The Montreal Just for Laughs comedy festival in 2005 and also The Kilkenny Cat Laughs festival in 2005 and 2006. He wrote TJ and TJ sketches on Today FM. His Edinburgh debut "Do not adjust your mind reality is a fault" received a five-star review from The Scotsman. He has previously co-hosted the Breakfast with Bernard and Keith show on the Irish radio station I105-107FM but on the 25 June 2011 he announced he would be leaving.