THE EFECT OF TBLT ON DEVELOPING ENGLISH LANGUAGE WRITING SKILLS OF PAKISTANI ESL LEARNERS AT UNDERGRADUATE LEVEL Rai Zahoor Ahmed ABSTRACT ESL learners play a vital role in the process of language teaching and learning at every level. The present study illustrates the effectiveness of Task Based Language Teaching (TBLT) on developing second language writing skills by the Pakistani ESL learners at the university undergraduate level. The study comprised twelve weeks of TBLT treatment to the BS level students in a Pakistani public-sector university. The major focus of the study was on improving ESL learners’ descriptive writing skill and the students wrote descriptive essays during the pretest at the onset of the experiment and in the posttest after TBLT intervention. Second language performance was measured through L2 performance triad i.e. complexity, accuracy and fluency. ESL learners wrote Weekly Reflective Journals to describe their opinions about TBLT treatment in terms of pedagogical perspectives to improve their English language writing skills. Students’ opinions written in the Weekly Reflective Journals consolidated the quantitative findings of the study during the pretest and the posttests in terms of L2 performance descriptors. The study concluded with the beneficial effect of TBLT treatment for improving writing skill as the students performed better in their L2 writing skills during the posttest as compared to their performance in the pretest. KEYWORDS: ESL, Task Based Language Teaching, L2 Performance, Writing Skills