Most students and practitioners commonly see grammar teaching and learning as both tedious and unattractive experiences. In this sense, more innovative ways of presenting foreign language grammar are needed. One such novel approach is Just-in-Time Teaching (JiTT), which has proven to be beneficial in a wide array of disciplines, including language learning. The present exploratory study aims to examine how JiTT contributes to success rates in English grammar learning at two proficiency levels, and to analyse how participants perceive this methodological approach. Sixty-four English as a foreign language students, divided into beginners and intermediate learners, were exposed to five JiTT grammar lessons throughout an academic semester. Participants' answers on JiTT quizzes and satisfaction questionnaires were recorded and compared to their performance on a final exam based on the same five grammar points presented through JiTT. Statistical analyses revealed that JiTT had little impact on learners' success rates in grammar learning, although a higher impact was observed in intermediate learners, in comparison to beginners. However, both groups of participants showed positive attitudes towards the intervention. Results are discussed in the light of how teaching English grammar through JiTT contributes to success rates. The potential of JiTT as a good methodology to be used in foreign language teaching is also addressed.