Constable returned to the Conference Premier after signing for Oxford United on 8 July 2008 on a season-long loan for 2008–09. He made his debut in a 3–0 defeat by Barrow on 8 August 2008, scoring his first goals in a 6–3 victory over Eastbourne Borough a week later, scoring twice and providing an assist. He scored both goals in a 2–1 victory over Northwich Victoria on 2 September 2008, which was Oxford's first away victory of the season. He picked up a groin strain during a 1–1 draw with Kettering Town, and was expected to be out of action for two to three weeks. He did not miss any matches through this injury, playing in a 1–0 defeat to former club Kidderminster. He scored the winning goal in a 2–1 victory over Burton Albion on 18 October 2008, which he said "was an absolutely massive result". Manager Chris Wilder said in January 2009 he wanted to extend Constable's stay the club, claiming he "epitomises what I am trying to build here at the club". With regard to extending his stay at Oxford, Constable said he was "open to offers". He gathered further praise from Wilder later in the month and there were calls from Oxford fans for Constable to be signed permanently.