ABSTRACT-The present study aims at investigating how Blog-Assisted Language Learning (BALL) can enhance EFL tertiary learners’ writing performance covering complexity, accuracy, and fluency through collaborative action research while at the same time it seeks to discover new knowledge that can inform the implementation of BALL in a writing class. This study employed Collaborative Classroom Action Research conducted in one cycle in one consecutive semester intended to make improvement in the teaching and learning of writing using BALL. There were 30 students of a university level majoring in English Education Department who joined Advanced Essay Writing Class in this study. The data were collected through interview, open-ended questionnaire followed by in-depth interview, and writing test. The findings showed that EFL learners improve their writing performance and they become more active in online class condition with two atmospheres: collaboration and competition among the learners. 
 Keywords: BALL, EFL Learners, writing performance, action research.