Language learners' productive role in teaching and learning processes has recently been the focus of attention. Therefore, this study aimed at investigating the effect of oral vs. written output-based instruction on English as a foreign language (EFL) learners' vocabulary learning with a focus on reflective vs. impulsive learning styles. To this end, 131 learners were chosen among 182 learners by taking Nelson vocabulary proficiency test. Next, the participants received a valid Persian version of reflective thinking (Kember et al., 2000) and Barratt, Patton and Stanford (1975) BIS (Barratt's Impulsiveness Scale) 11 impulsiveness questionnaires, based on which both experimental groups were divided into impulsive and reflective subgroups, but the control group consisted of both impulsive and reflective learners. After 15 sessions of intervention and based on the results through one-way ANOVA and independent t-test it was concluded that both oral output and written output had significant effect on vocabulary learning of reflective and impulsive EFL Learners. It was also observed that the effect of both oral output and written output on impulsive (oral group's mean = 21.04; written groups' mean = 21.75) learners and reflective learners (oral groups' mean = 22.38; written group's mean: 22.23) is not significantly different. Pedagogical implications are discussed.