In 1854, the Company of West Switzerland gained a concession from the canton of Vaud for the construction of a railway line from Lausanne to Yverdon, with a proposal to continue via Payerne and Murten to Bern.

On 10 June 1857 a section from Villeneuve at the western end of Lake Geneva to Bex in the Rhone Valley opened.

On 7 November 1859, the section from Yverdon to Vaumarcus was opened, connecting the OS was to the network of the Franco-Swiss (Franco-Suisse, FS).

On 25 June 1858 the OS connected with Geneva with the opening of the Versoix–Geneva route of the Geneva–Versoix Railway (Chemin de fer Genève–Versoix, GM).

Because of their financial difficulties, the three western Swiss railways established a joint business called the Association des chemins de fer de la Suisse Occidentale (association of the railways of western Switzerland) on 1 January 1865 after lengthy negotiations.