Quality of Classroom Life is considered as a serious issue in academia around the world, and it has recently received global inquiry in EFL and ESL contexts. However, no questionnaire has been developed to assess the Iranian students’ and teachers’ attitudes towards the quality of life in the classroom. After developing a conceptual framework, the final draft of the developed questionnaire with 71 items was administered to the main sample of participants (n=150). An Exploratory Factor Analysis was performed to identify the components of the instrument, followed by Confirmatory Factor Analysis to measure its construct validity. As a result, the final draft of the Quality of Classroom Life Questionnaire comprised 71 Likert-point items. In phase 2, a number of EFL students and teachers (50 teachers and 322 students) participated in the study which was intended to observe the impact of Modular Instruction on the Quality of Classroom Life. Findings of the study suggested that: (a) the Iranian students and teachers had highly positive attitude towards the Quality of Classroom Life, and believed that educational view, teaching quality, classroom environment, classroom management, quality of classroom interactions and puzzle content played a crucial role in exploratory practice; and (b) the modular instruction which was the descendant of Postmethod instruction had a positive impact on the Quality of Classroom Life. The findings promise implications for teachers and teacher educators as well as the materials developers as the knowledge of classroom quality and modular instruction can enhance their understanding of the nature and conditions of learning.
