This paper aimed to develop and validate the Zero Textbook Satisfaction Scale (ZSS), a measurement tool to assess student satisfaction with Zero Textbook Costs (ZTC) resources. The validated ZSS is available via a CC BY-NC-ND license and is a valuable tool for faculty and institutions seeking to understand student perceptions of their OER/ ZTC adoptions and for broad scale OER/ZTC adoption initiatives seeking to understand student experiences with materials across a wide variety of courses. The ZSS was administered, revised, and validated following DeVellis (2017) 8 steps for validating measurement tools. The secondary data was analyzed using Exploratory Factor Analysis (EFA), which resulted in 11 items on 1 factor and a Cronbach's alpha, which showed excellent internal consistency ([alpha] = 0.94). The ZSS validated tool is designed to be used by faculty who would like to assess student satisfaction with the open source textbooks, and compare data to other sites of adoption.