Purpose: Who is the most effective agent when giving indirect written corrective feedback (IWCF) to English as a foreign language (EFL)? The answer is ambiguous, and factors such as gender have been neglected. For these reasons, this study attempts to reveal the most effective agent when giving IWCF and seeks to highlight the impact of gender when receiving IWCF from different agents. Method: A quasi-experimental study was carried out in which the participants were three classes of EFL learners studying at a private university's preparatory school. One of the classes was named class A, which only recieved instructor IWCF, another class B, which only recieved peer IWCF, and the last class C, which only recieved collaborative IWCF for a five-week period. Each group produced five written texts regarding the same topic each week at the same time. The data, or the participants' texts, were analyzed quantitatively. Findings: It was revealed that class C--who received only collaborative IWCF--significantly improved their writing skills compared to the other classes that received teacher and peer IWCF. In terms of gender, it was revealed that the male participants performed better than the female participants in class A, and the female participants in classes B and C produced better written texts compared to the male participants. Implications for Research and Practice: Pre-service and in-service teachers should provide IWCF to their EFL learners collaboratively, and they should consider the gender factor. It is suggested that future research focuses on other factors (i.e. age, proficiency). It is also suggested that researchers focus on the other type of feedback, namely direct written corrective feedback.