The Oskar Reinhart Museum is located in a 19th century building that was constructed by the Zurich-based architect Leonhard Zeugheer (1812–1866). It was built between 1838 and 1842 in Neo-Renaissance style for use as a boy's school in the city of Winterthur. In its first function, it housed the boy's school, the vocational school, the city library with its museal collections. The building was used by the municipal authorities between 1928 and 1939.
From 1948 to 1951, the building was converted for the Oskar Reinhart Foundation Collection in accordance with architectural plans by Sträuli and Rüegger. It was officially opened on 21 January 1951 as “Museum Stiftung Oskar Reinhart” [Museum Oskar Reinhart Foundation] in the presence of the Federal Council. This makes it the oldest collector's museum in Switzerland. Until his death Oskar Reinhart was involved in continuously reorganising the collections in the Museum and presenting them according to subjective and formal criteria. In the Deed of Foundation, Reinhart expressed the desire not to change his concept of presenting the collections after his death. Between 1993 and 1995 the Museum was refurbished by the architect Johann Frei and extended with an addition exhibition room on the top floor. During this process the colour schemes in the collection rooms were also redesigned and painting hangings were rearranged in accordance with art history guidelines. Unfortunately, reconstructing the original Oskar Reinhart picture hangings was only partially possible. This is because their original presentation was not documented before they were taken down and because only a few pictorial documents were kept from the 1950s to 1970s. Stefan Lauper, a Geneva-based art historian, is currently researching the history of the various ways collections were presented at the Oskar Reinhart Museum under the direction of Prof. Dr. Dario Gamboni at the University of Geneva.