Classroom-based research (CBR) in second and foreign language education takes place in authentic classroom settings, where researchers have limited control over variables. Unlike laboratory-based studies, CBR focuses on real-world learning environments and has evolved into a systematic field of inquiry. It encompasses both learner-focused studies, which explore learning processes and outcomes, and teacher-focused studies, which examine pedagogy, practices, and beliefs. In the context of Literacy Education and Second Language Learning for Adults (LESLLA), CBR provides valuable insights into language learning, literacy development, and social participation. Despite growing interest in this area, methodological approaches remain underexplored. This article reports on four studies conducted in Canada and Australia illustrating different research designs within the CBR framework. The different research designs and their contributions to LESLLA scholarship are discussed and analyzed, followed by a discussion of lessons learned through implementing CBR in diverse contexts. By reflecting on research experiences, we highlight methodological strengths and challenges, offering insights to support the advancement of evidence-based practices for LESLLA learners and educators.