As part of a larger museum experience, in-gallery technology can help ‘visitors’ think in new ways and engage with different perspectives. However, technology also needs to meet ‘user’ needs for easy and intuitive interaction. While many institutions excel at studying their visitors’ goals and wants, traditional methods may fall short when the museum experience includes digital interfaces. In this presentation, Centralis' Kathi Kaiser and Tanya Treptow explore how in-gallery usability testing may address this critical gap in the museum evaluator’s toolkit. Drawing on examples from our studies at Chicago’s Field Museum and other immersive environments, we illustrate how evaluators can go beyond measuring visitors’ opinions to examining their actual interactions with digital technology, and how those interactions may contribute to or distract from their learning and enjoyment. This talk provides practical guidance for running in-gallery usability studies, including tips for recruiting participants, designing a test plan, recording sessions, and interpreting the findings.