Gross was a lawyer and lecturer of Constitutional and Administrative Law at the University of St. Gallen. From 1979 to 1987 he was a member of the city council ( executive) of plug- Born. Between 1980 and 1984 he was a counselor of the canton of Thurgau and also the President of the SP Thurgau in the large. Of the 1995 elections until his death in 2005 he was a member of the National Council. He was a member of the Commission for Social Security and Health (1995-2005), the Committee for Legal Affairs (1998-2003) and the State Affairs Committee (2003-2005). From 1992 to 2004, Gross President of the Swiss Society for Health Policy ( SGGP ). From 1994 he served as president of the canton of Thurgau Trade Union Confederation and the Foundation Pro Mente Sana in Weinfelden.
On May 6, 2005, he collapsed during a Parliamentary Football Tournament in Waldenburg together against the team of the German Bundestag. Despite immediately initiated resuscitation only his death could be established at the hospital in Schwäbisch Hall.
His successor in the National Edith Graf- Litscher is, which was sworn in on 30 May 2005.