This thesis investigated the use of grammatical cohesive devices in the reading texts of an Indonesian ELT textbook, specifically "Work in Progress" for tenth-grade high school students. The current study attempted to: investigate the types of grammatical cohesive devices, determine the percentage of grammatical cohesive, and find out the most dominant grammatical cohesive devices used in reading the texts of the “Work in Progress” textbook. The framework for grammatical cohesive devices developed by Halliday and Hasan (1976) was applied to the analysis of the reading texts. Content analysis was used to analyze the data. The findings revealed 448 grammatical cohesive devices were used in reading texts of English textbooks. The grammatical cohesive devices were distributed into 72.99% reference words (327), 1.34% substitution words (6), 7.81% ellipsis constructions (35), and 17.86% conjunctive words (80). Further, the references consisted of 242 personal references, 76 demonstrative references, and 9 comparative references. Three nominal substitutions and three verbal substitutions with no clausal substitution were found in the textbook. While the use of one nominal ellipsis, 26 verbal ellipsis, and 8 clausal ellipsis were also found in the textbook. Conjunctions found in the textbook constituted 47 additive conjunctions, 10 adversative conjunctions, 5 causal conjunctions, and 18 temporal conjunctions. Understanding the distribution and use of these devices can aid teachers in creating varied and engaging teaching activities, enhancing students' understanding and interpretation of reading texts.
