The present study aimed to investigate the readability of reading passages in elementary school textbooks with focus on lexical, syntactic, and cohesion features. Toward this end, the relevant features of reading passages in the five English textbooks currently in use in elementary schools were analyzed. Comparisons of the textbooks for different grades were also made in terms of these features. In lexical features, significant differences were observed between grades in a way that readability decreases as grades advance. As for syntactic features, the textbooks were found to have areas for improvement, especially in noun phrase density. At the cohesion level, little consistency in progression in terms of cohesion features was observed between the textbooks for each grade. These findings suggest a need to give a more systematic attention to cohesive features in the process of developing and evaluating textbooks for different grades.