Scholars of legal translation have shown particular interest in the methods of multilingual legislative drafting that are used in several national and international institutions. The origin of these methods is usually traced back to Canada in the late 1970s. However, a prefiguration of co-drafting practices can be found in Switzerland several decades earlier: by the First World War, this officially multilingual country had already experimented with sophisticated measures to improve the quality of legislative translation. As there is only fragmentary knowledge of this historical precedent, this article proposes to study it in greater depth, with a view to explaining its lack of visibility in Legal Translation Studies. The study covers the period from the midnineteenth to the mid-twentieth century and is based on digitized institutional archives. It shows that the Swiss legislative process routinely involved collective bilingual work in German and French, including forms of co-revision and co-editing. It also shows how political factors contributed to the integration of Italian, the third official language. By contrast, the article places the emergence of the contemporary concept of co-drafting in its historical Canadian context. The conclusion highlights the potential contribution of such historical research to critical approaches to legal translation.