This research presents an inaugural general method of measuring the collaborative and confrontational interoperability of a heterogeneous set of systems in the context of an operational process. The method is holistic, fundamental, flexible, and mathematical in nature and accommodates all types of systems and interoperations. The method relates the interoperability measurement to measures of operational effectiveness for confrontational operational processes. Extant leveling methods of describing interoperability are shown to be a special case of the more general method given in this research and the general interoperability measurement method is demonstrated through the presentation of coalition interoperability, suppression of enemy air defenses, and precision strike applications. Further application is recommended in technical, non-technical, cross-domain, and non-traditional interoperability areas and additional research is suggested on the topics of indirect interoperability measurement and collaborative interoperability impact on operational effectiveness.