Online language learning is becoming increasingly popular with advances in technology that facilitate the acquisition of language in virtual environments (Duensing et al., 2006). Much of the recent literature on online foreign language instruction has focused on the possibilities presented by online technologies but has failed to examine the practical side of how and by whom online language courses are delivered. Several authors have published articles on the skills needed to be a successful online language teacher using empirical approaches (Comas-Quinn, 2011; Ernest et al., 2013; Shelly et al., 2006) and some focus more on the theoretical discussions (Compton, 2009; Hampel & Stickler, 2005). The current study drew on the existing frameworks in the previous literature to operationalize and measure the participants' online language teaching skills while they taught a class online. These participants were graduate student instructors of Spanish at a large public university (n = 3). Using a case study approach to data analysis (Duff, 2008), and gathering data through a background questionnaire, pre-and post assessments, bi-monthly teaching journals, self- and researcher observations, an exit survey and a semi-structured post-interview, this study investigated how the participants' online language teaching skills, proposed by Hampel and Stickler (2005) and Compton (2009), changed over the course of them teaching an online language course and the factors that seemed to influence more or less development in each skill area. Additionally, it compares the main findings from this study with those found in previous literature and offers recommendations of how to promote the development and sustainability of these online language teachers' skills. This study serves as one of the few empirical studies conducted in the United States that concretely operationalizes and measures through carefully designed instruments the prescribed online language teaching skills in an effort to gain insights into what contributes to their development and how to sustain their continued growth.