Students at the tertiary level need arguments because they are expected to use analytical and critical thinking skills. The present study is situated in an English as a Foreign Language (EFL) context in an Omani University and reports the experience of (N=46) undergraduate EFL writers in argumentative essays and persuasive posters. Using rhetorical strategies, and drawing on the principles of persuasive writing, the participants prepared posters and essays on two separate topics. Data were collected from the 46 participants’ responses to a semi-structured online survey questionnaire. Analysis of the data obtained indicates that the participants preferred designing posters to writing persuasive essays while reporting varieties of rhetorical difficulties in building an argument for persuasion. The participants also perceived establishing evidence and facts as the most challenging element in persuasive writing and arousing the audience’s feelings and emotions as the most challenging rhetorical appeal in posters. Some pedagogical implications were reported as well.