Integrating outcome-based elements like advanced communication, productivity and accountability, critical thinking, creativity, collaboration, flexibility, and adaptability is considered vital in a textbook. However, evidence has shown gaps in specific areas of textbooks, as illustrated by the "Bahasa Inggris Grade XII" textbook, which lacked advanced teamwork and communication skills. This research aims to evaluate the incorporation of outcome-based education in the textbook through the application of Spady's theory. Utilizing data on the text unit order, the current study employed a descriptive qualitative research framework and acquired data through a Likert scale. The findings disclose that various aspects of outcomebased education are thoroughly addressed in this textbook. Nonetheless, the collaborative component and the intricate communication aspect are conspicuously absent as denoted in chapter 3 and chapter 4. A mere forty-seven percent of the content in the textbook "Bahasa Inggris Grade XII" has been assessed and meets the criteria of outcome-based education. The textbook serves as an excellent case study to evaluate and enhance the integration of OBE principles in high school EFL materials in Indonesia, offering a basis for improving educational outcomes during a crucial period in students' academic and personal growth. This level of attainment, which falls below expectations, indicates a lack of complete adherence to the principles of outcomes-based education within the English textbook. As this ongoing research carries significant implications for those involved in developing and writing curricula. It is recommended that the textbook aligns with Spady's concept of Outcome-Based Education (OBE), addressing gaps such as the lack of emphasis on teamwork and complex communication aspects. To enhance the achievement of educational objectives, authors are advised to pinpoint areas for enhancement through collaboration with educators, students, and curriculum experts.