The present study attempted to probe into the effects of four planning time conditions (pre-task, extended task, free writing, and control) over the frequency of employing metacognitive strategies in argumentative and expository writings of 108 participants. Employing an experimental writing task design under four planning time conditions and implementing a retrospective questionnaire, both qualitative and quantitative approaches were adopted. Through implementing the retrospective questionnaire, an 8-point Likert-type scale was used and the associated statistical procedures were employed. The results showed that the frequency of the use of Generation of Ideas strategy was significantly higher in the argumentative writings than in the expository writings. The use of Elaboration of Ideas strategy was significantly different from Thinking about Language Aspects strategy and Thinking about the Essay Structure strategy and it was the lowest. The highest strategy use belonged to ‘Thinking about Language Aspects strategy’, followed by Thinking about the Essay Structure, Generation of Ideas, Organization of Ideas and Elaboration of Ideas strategies respectively. The use of ‘Thinking about Language Aspects strategy’ in the extended task condition was different from the other groups, and it was the lowest. In ‘Thinking about Language Aspects strategy’ use no significant differences were observed among argumentative and expository writings. The study can help broaden the understanding of EFL writers’ metacognitive writing processes involving planning and, the results may have pedagogical implications for EFL writing instructors and theoretical implications for EFL writing researchers.