This paper presents an exploratory action research study carried out by two English as a foreign language teachers in a private, non-profit institution in Bogota, Colombia, with a group of 12 learners in a B1 English course. These students faced difficulties elaborating on their ideas when discussing issues in class. The study placed emphasis on the use of argumentation outlines and peer assessment to boost learners' argumentative abilities. Audio-taped conversations and open-ended interviews were used to understand the impact on the pedagogical intervention. Findings revealed that argumentation outlines and peer assessment can promote learners' awareness and ability to engage in argumentation processes. Moreover, peer assessment appears to be an essential tool for enhancing personal and collaborative learning, as well as for promoting learner reflection and agency.