Learning English proficiently specially in English as a foreign language (EFL) context needs developing proficiency in all four language skills (listening, speaking, reading, and writing). Knowing four language skills helps language learners to learn the language faster and more fundamentally. Teachers and textbooks as the important sources of materials in EFL education play vital roles to improve students' language skills. Improving language skills need learners' active participation. Task-based language teaching (TBLT) as an important concept in language teaching method is very helpful to develop learners' integrated language skills. In this study, a descriptive qualitative approach, using content analysis of the textbook, was used to evaluate Iranian tenth-grade senior high school English textbook Vision1 in terms of four language skills activities based on Willis' (1996) task-based lesson plan model. A questionnaire adapted from Wuttisrisiriporn and Usaha's (2019) was also administered to 107 (51 males and 56 females) first-grade senior high school English teachers to evaluate their perceptions towards four language skills activities in the textbook. Findings regarding the textbook analysis indicated that it does not adequately include four language skills activities. Considering teachers' perceptions towards Vision 1 skills activities, the findings revealed that most of the teachers disagreed with the adequacy of the four language skills activities. Based on the findings, it is suggested that appropriate language skills activities should be included in Iranian tenth-grade English textbook to enable learners to interact accurately and fluently. In this regard, the study provides some helpful guidance which might be useful for Iranian English language material developers and teachers of tenth-grade senior high school to reconsider the textbook content
