This study examined the effect of rehearsal, strategic, and online planning on the intermediate undergraduate EFL learners’ writing complexity, accuracy, fluency (CAF), lexical variety, and the cognitive psychological performance of attentional allocation to linguistic aspects during planning . To this end, 80 intermediate university students were randomly divided into three experimental groups and one control group. The participants’ performance was compared based on measures of Wigglesworth and Storch’s (2009) fluency, Storch and Wigglesworth’s (2007) accuracy, Foster and Skehan’s (1999) complexity, McKee , Malvern, and Richards’ (2000) vocd-D model of lexical diversity. The study focused on rehearsal, strategic, and online planning in argumentative writing tasks. Retrospective interviews were conducted right after task performance to examine the participants' attentional allocation under three planning-time conditions. It was revealed that rehearsal task planning resulted in higher CAF and lexical variety in comparison to the other groups. Noticeable variation was also evidenced in the participants’ attentional allocation in terms of CAF across different time planning conditions. It was also shown that the learners paid more attention to the conceptualization of ideas during pre-task planning through sentences or clauses while performing a task. Little attention was paid to formulizing complex or accurate utterances. The findings have numerous pedagogical implications for EFL teachers, university instructors, and EFL students.
