The aim of the current study was to compare the influence of on-line planning and pre-task planning on the performance of EFL university students enjoying different levels of proficiency regarding accuracy, fluency and complexity. To this end a group of 134 EFL learners with different proficiency levels were asked to write narrative tasks under two planning conditions (Pre-task planning and on-line planning). The results of the investigation showed that neither on-line nor pre-task planning affected the accuracy of writing. It was also revealed that on-line planning led to more fluent written language than what pre-task planning did, and that pre-task planning, compared to on-line planning, caused the students to produce more complex written language. Another finding of the research was that students with higher proficiency levels outperformed their low-proficiency counterparts considering accuracy, fluency and complexity during both on-line and pre-task planning. In other words, no interaction was found between planning conditions and proficiency levels.