The past 40 years have witnessed significant developments in ELT research, reflecting the changes in learners' language needs and the extensive development of various language learning/teaching methods in different times and places. The aim of this study is to provide a systematic and comprehensive account of changing ELT methods (oral-structural approach, communicative language teaching and task-based language teaching) in Hong Kong's secondary education between 1975 and the present. By adopting Richards and Rodgers's (2014) framework (approach, design and procedure), it examined how ELT theories have been transformed into local curricula (1975, 1983, 1999 and 2002/07) and commercial textbooks (Longman, Oxford University Press) via detailed content analysis. The findings suggest that research into ELT methods in Hong Kong over the past decades has generally directed the designs of the language curricula. Changes in the textbooks, however, have been relatively limited, although considerable attempts have been made to align textbook design with ELT trends. By considering various constraints in the theory-to-practice process, this study offers suggestions for future research and language teaching, particularly regarding the recent debate over the choice between the 'weak' and 'strong' versions of task-based language teaching in EFL contexts, and the post-methods perspective in language teaching.