This article presents two case studies that show how learner involvement and collaboration in assessment are valid pedagogic tools to encourage learner reflection and engagement, particularly where a very traditional approach to language learning is the norm. The authors, who teach in universities in Japan, discuss different but related approaches to assessment in CLIL (Content and Language Integrated Learning) classrooms. The first case study describes how assessment in the classrooms in focus requires more engagement on the part of learners as they must work things out for themselves. Collaborating with classmates, which entails discussing assessment decisions, can foster language development. If learners engage in informal discussion about their learning performance, they can review previous learning, affirm progress, and make suggestions about future learning goals and how to improve their learning outcomes. In the authors' view these processes help learners to develop self-regulation and self-efficacy. The second case study involves students developing collaboration skills during project work in which they are also involved in the assessment process. They give slide and poster presentations, write reports, and analyze scientific information while collaborating with their classmates. During this process they are also responsible for self- and peer-assessment. As a result of their collaboration they acquire language, but they also develop the ability to collaborate further. The article concludes by briefly discussing learner involvement and collaboration, and the central role that feedback practices can play in learning.