Discussion essay plays a crucial role in academic writing. It has been proven to enhance students' analytical and critical thinking skills effectively. However, students often struggle to compose a good writing due to their inability to use the language features. In that regard, this study aims to identify students’ weaknesses in the discussion essay and the changes seen after the intervention. The study used a purposive sample of 10 first-year students from the Computational Science Programme in Universiti Malaysia Sarawak (UNIMAS) who took Academic English 2 as an elective course. The study adapted the four stages of action research proposed by Mertler and Charles (2005). It administered a pre-test, post-test and an observation on the students. The findings indicate a significant decrease in the frequency of errors in the language features, namely verb, persuasive language and technical terms, after the two-month intervention. Students also exhibited positive learning behaviour throughout the intervention by participating actively in the learning activities.