Building on a historical case study on the first two stock exchanges to adopt the now globally dominant for-profit organizational form, the Stockholm Stock Exchange in 1993 and the Helsinki Stock Exchange in 1995, we argue that interaction among socially proximate peers contributes to pioneering organizational form adoption within an industry, particularly when such forms are introduced by established organizations. Peer interaction can induce a search for technically efficient organizational forms through the sharing of collective experiences, the establishment of collective assumptions, and a joint search for solutions. Together, these factors contribute to the legitimization of novel organizational forms in the local setting before the adoption of the first instantiation of those forms. We propose a context-sensitive multilevel model of peer-interaction-induced pioneering organizational form adoption that considers shared macro environmental drivers, idiosyncratic local environmental drivers, and peer interaction as central social mediators between the two.