In 1986 he was appointed an Auxiliary Bishop of Regensburg. On 8 March 1986 he was created titulary bishop of Munatiana. On 13 December 2001 he was appointed as bishop of Passau and installed on 23 February 2002.
Following canon law, Schraml offered his resignation to the pope in 2010, upon reaching the age of 75. He retired on 1 October 2012.
- Bischof emeritus Wilhelm Schraml spendet Firmlingen den Segen, Heimat Zeitung, 4 July 2014