The present study examines the interactions of writer’s and rater’s argument positions on the prompt in scoring L2 argumentative writing. Four Korean EFL raters scored essays composed by sixty eight Korean EFL university students. Their scores were statistically observed and analyzed according to the argument positions of writers and raters. Results of the study revealed that the majority of the students wrote supporting argument essays and yet, their scores were lower than those who wrote counter-argument essays. Although there were no statistically significant variations observed from the argument positions of writers, the raters assigned higher scores to the latter, assuming higher task difficulty and greater proficiency of the writers. Rater group variations were found depending on the assessment dimensions and the essay’s argument positions, though no statistically significant interactional effects were noted by the argument positions of writers and raters. Score variations were further revealed within each of the rater groups when they rated essays written from the same position as theirs. The study shows the interplay of writer’s and rater’s positions in scoring EFL argumentative essays and concludes that the rater’s positions can be the important sources of rater variation which influence their perceived task difficulty and final scores with implications and suggestions for further research.