His initial outings in the first team displayed some promise as well. He made his first-team debut on 3 January 2004, coming on as a second-half substitute in a 2–0 FA Cup victory against Notts County. His Premiership debut came four months later, when he replaced Stewart Downing in a 5–1 defeat away at Portsmouth on the final day of the 2003–04 season. Morrison's first European action for Boro was on 30 September 2004 in a UEFA Cup tie away at Banik Ostrava. He marked the occasion by scoring his first goal for the club, a last-minute equaliser that secured a 1–1 draw in the second leg and a 4–1 aggregate victory. Morrison started for Middlesbrough in the 2006 UEFA Cup Final against Sevilla. On 19 March 2007, he was sent off in an FA Cup quarter-final replay against Manchester United for a kick out at Cristiano Ronaldo.