► We integrated user-centered and participatory design approaches into our research. ► We used mixed methods research to collect data for our work on the Purdue OWL. ► We worked with participants using adaptive technologies to access the Purdue OWL. ► Results indicated that the Purdue OWL was accessible but not sufficiently usable . ► We used findings to improve the Purdue OWL and to work with campus organizations. This article discusses issues of accessibility and how user-centered and participatory approaches can inform empirical research to guide the Universal Design of virtual spaces and influence writing center efforts for students with disabilities. Because this article describes how to integrate usability/accessibility testing for online and in-person services, it can work as a model for writing centers struggling with the challenges of serving students with disabilities. Toward this end, the article discusses two generations of usability testing on a large, well-established online writing lab (the Purdue OWL), as well as the collaborative projects that emerged between the usability team and campus disabilities services as a result of this testing. The article concludes with heuristics and generative questions that may assist readers in developing similar projects tailored to their own contexts.