Blog use may offer instructors a helpful tool for teaching writing at the tertiary level in Teaching English as a Foreign Language (TEFL) classrooms. This article reports on a quasi-experimental study regarding the effect of blog-centered writing instruction on students' writing performance. Fifty intermediate English students at a Turkish university participated in the study. The control group (n = 23) received in-class process-oriented writing instruction and the experimental group (n = 27) integrated blogs into their writing processes by using a blog software. Based on the analyses of students' written work, the findings suggest that blog-integrated writing instruction might have resulted in a greater improvement in students' writing performance than merely in-class writing instruction. The study therefore supports the conclusion that English as a Foreign Language practitioners' use of blog software has potential to promote more effective writing instruction. (Contains 5 tables, 4 figures and 1 note.)