This study explored how task complexity, writing behaviors (i.e., pausing and revision behaviors), and writing performance (i.e., task completion, coherence and cohesion, language use, and expression and tone) influence and relate to each other. Thirty advanced-level Korean EFL undergraduates completed writing tasks differing in complexity. A combination of keystroke logging and stimulated recall interview was employed. It was found that the simple task group showed a greater number of pauses and revisions related to lower-order writing processes, whereas the complex task group showed longer pauses related to higher-order writing processes. While task complexity had no influence on writing performance, writing behaviors revealed significant relationships with text quality. In the simple task group, pause length and revision were negatively related to writing scores, whereas pause frequency revealed mixed results. In the complex task group, consistent negative relations were found between pausing behaviors and text quality, and fewer revisions were related to better scores in expression and tone.