This study aims to investigate whether there is any one of the skills that is developed more than the other skills after using the coursebook "Yes You Can A1.2" published by Ministry of National Education (MONE). Differing from the previous studies on integrated skills, this study tries to find out whether there is integrated skill bias in the coursebooks although they are prepared with the claim that they are integrating the four skills and aiming to develop all of the four skills equally. To fulfill this aim, a pre- and post-test, aiming to see whether there is change in students' proficiency in four skills after using the coursebook; a student questionnaire and a teacher questionnaire, aiming to determine their perceptions on the efficacy of the coursebook in terms of four skills, were developed and administered to 9th grade students. Besides, a focus group interview was conducted both with the students and the teachers to triangulate the findings. The findings indicated that students are content with the coursebook while teachers are not in terms of its efficacy in bettering students' four skills. In addition, the results revealed that "Yes You Can A1.2" is reading dominant or reading biased in terms of teaching four skills.