Although L2 writing has attracted salient attention and monopolized many studies in EFL contexts, there is still no full image of its complicated nature. Trying to play a supplementary role in achieving that image, this study aimed at finding whether Persian and English argumentative and descriptive academic writings were inter/intra-lingually associated and if genre played a role in provoking any differences in the means of total scores obtained from the essays. In so doing, 50 Iranian senior MA TEFL students at the intermediate level were asked to write down two argumentative and two descriptive essays in Persian and English. Each essay was assessed against IELTS task 2 writing band descriptors. Then, the data were analyzed through the Pearson product-moment correlation and paired-samples <em>t</em>-test. The results revealed there were significant positive correlations between the total scores obtained from Persian and English argumentative and descriptive essays. The findings supported the existence of a common underlying proficiency (Cummins, 1980), out of which L1 and L2 writing skills emerged. The results also illustrated there were significant differences between the means of some of the total scores. It was supposed these differences might be due to the possible genre-sensitive nature of common underlying proficiency.
