The purpose of this study was to investigate the utilization of textbook adaptation strategies by novice and experienced EFL instructors working in a language preparatory program at a foundation (non-profit, private) university in Turkey. Specifically, the study investigated the self-reported beliefs of the two groups of instructors about textbook adaptation and explored which adaptation strategies were most frequently implemented in their classroom. The study also attempted to compare whether there were differences between the two groups of instructors related to their use of adaptation strategies in their courses and find out the reasons behind their adaptive decisions. The participants were 14 Turkish EFL instructors (7 novices and 7 experienced) offering English courses in an intermediate level English classroom. Data were collected from reflective essays, lesson plans, and semi-structured interviews. The findings revealed that both groups of instructors shared highly positive beliefs about the implementation of adaptation strategies in their courses apart from some differences related to types of strategies and their frequencies. Besides, the adaptive decisions of the participating instructors were closely related to their students, tasks, context, time, and their own beliefs. Based on the obtained findings, the researchers provided some pedagogical implications and suggestions regarding the effective use of textbook adaptation strategies in language preparatory programs.