As the disciplinary focus on learner agency and autonomy increases, a space for online writing labs (OWLs) is reemerging. OWL services represent an opportunity for writing centers to expand their reach both on and off campus, assisting student writers where they are at and in a way that allows them to take increased agency over their compositional processes and products. In addition, while US-based OWLs have a long history and many useful resources, they cannot speak to the needs of students writing in the English as a foreign language (EFL) context and for different academic purposes than their peers studying at U.S. colleges and universities. Despite this difference, there has been little scholarship that has examined OWL development best practices. This article, hence, uses the author's experiences as an administrator at one of the world's oldest and largest OWLs, the Purdue OWL, to provide writing center practitioners in EFL contexts with a theoretical and practical toolkit for starting up OWL services. This includes issues of fitting the OWL service into the scope of the writing center's mission and considering the degrees of responsiveness and interactivity that the writing center can meaningfully provide. Also addressed are issues of content development as they have been informed by the fields of user experience design (UXD), L2 writing, and computers and composition. Recommendations for future research and scholarship are also provided.