Organizational design is an important topic in the literature on organizations. Usually the design principles are addressed informally in this literature. This paper makes a first attempt to formally introduce design operators to formalize the design steps in the process of designing organizations. These operators help an organization designer create an organization design from scratch as well as offer the possibility to revise existing designs of organizations. The operators offer both top-down refinements and bottom-up grouping options. Importantly, the operators can be combined into complex operators that can serve as patterns for larger steps in an organization design process. The usability of the design operators is demonstrated in a running example. The contribution of this paper provides a solid basis for the development of a software environment supporting interactive organization design processes. This is demonstrated by an implemented prototype example tool. © 2012 Elsevier Ltd. All rights reserved.