In addition to his work with Grinspoon, Jamieson co-wrote tracks for United States group Unwritten Law including "Elva" and "Nick and Phil" on "Elva" (January 2002) and "She Says" and "Because of You" on "Here's to the Mourning" (February 2005). Late in 2004 Jamieson was the lead vocalist for "Evie" part three, "I'm Losing You", by super group, The Wrights, which performed a cover version of Stevie Wright's 1974 hit. They issued it as a single which peaked at No. 3 on the ARIA Singles Chart in March the following year. In early 2005 Jamieson performed guest vocals on the track, "Sayonara", for the film "Deck Dogz".