This article presents a study on in-service professional development of Lithuanian secondary school language teachers. The motivation is based on the understanding of language education as a highly interactive, complex process that requires a teacher’s digital literacy skills combined with integrated instructional approaches. This requires the implementation of a set of professional development activities. As a research methodology, we use a mixed method approach based on collecting eye tracking data in the first phase and, then, focus on comparative teacher self-reflection using data analysis and qualitative interviews. Finally, based on the collected qualitative and quantitative data, educational experts develop and present recommendations on the scope and direction of professional development. As a result of this study, a comprehensive set of the eye tracking data from the experiment involving 93 participants in total and 23 recorded lessons is presented. This includes variables such as number of visits, time to first fixation, number of fixations, and fixation duration vertically and horizontally. The discussion presents the results of the qualitative part of the study, including comprehensive teachers’ feedback. In conclusion, an integrated training program for in-service language teachers is presented, including an eye tracking experiment that provides data for extensive self-reflection and feedback.