ATEF, AMIR2018-02-262018-02-262017-062015101133http://bspace.buid.ac.ae/handle/1234/1108This study investigates the different effects of task complexity on language performance and production in ESL classrooms. The researcher adopts the qualitative approach which is very suitable for such a study in SLA to gain detailed insights based on the actual speech production by L2 learners in task based language production. The study measures the impact of increasing task complexity on students’ oral production in terms of fluency, vocabulary, and grammar. The researcher used the IELTS speaking band descriptor as a reliable tool of assessment and a criterion of evaluation. The oral production of participants was evaluated by other examiners to ensure the high level of accuracy in terms of findings analyses that show positive impact on lexical resource in high achievers and a negative impact on grammatical range in mid-achievers.enlanguage performanceESL learnersDissertation