Textbooks need to be written in such a way that their readers can understand the written texts. One way of ensuring this objective in first grade textbooks would be the use of basic vocabulary, as determined by Ne'matzadeh, et.al. (1384). Considering the importance of the Quran textbook, and the need for students full comprehension of its text, the extent of the use of this vocabulary could be an index of its effectiveness. Of 137 words identified as basic, only 13 were observed in the first grade's Quran textbook! Such low frequency of the basic vocabulary could cause learning difficulty for the learners. However, the texts could easily re-written using the basic vocabulary.