This study analysed the implementation of Genre-based Approach and Differentiated-Instruction represented in reading tasks in an English textbook entitled Buku Bahasa Inggris Work in Progress published by the Ministry of Education and Culture, Indonesia. The researcher analyses the Genre-Based Approach and Differentiated-Instruction of reading task in the EFL textbook using content analysis method. However, the previous research indicates that the Genre-Based Approach in the textbook is not proportional. The objective of this research is to see whether the learning outcomes in textbooks are in accordance with the learning objectives in Genre-Based Approach. The writer used the GBA framework based on Feez and Joyce (1998) to analyse the implementation of GBA in the textbook. The finding showed that all of the GBA stages in reading tasks in the textbook are proportional. This study suggests a larger scale of research, such as investigating more than one textbook, involving more than one level of education, involving other English skills, and involving students or teachers in the next research in order to bridge their experience and their needs.