This chapter presents a subset of results from a study that explores source-based writing skills in pre- and in-service English language teachers from Antofagasta, Chile. This exploratory study was conducted during an advanced academic English course offered at a university in this city over two consecutive semesters in 2021 and 2022. The qualitative data from verbal protocols and interviews were analysed following a thematic analysis approach and the essays were analysed using a coding rubric covering different aspects of source use. The overall results revealed that while there is evidence of students’ enhanced awareness and skill with some formal aspects of direct quoting and paraphrasing, other aspects of source-based writing, such as understanding core information in the sources and effectively integrating that information into their essays, remained problematic for some students. Findings suggest that more extended and consistent scaffolded instruction may be needed to foster the development of more complex and sophisticated academic literacy skills.