To reveal what is being learned during the gaming experience, this report proposes an approach for embedding assessments in immersive games, drawing on recent advances in assessment design. Key to this approach are formative assessment to guide instructional experiences and evidence-centered design to systematically analyze the assessment argument (including the claims about the learner and the evidence that supports or fails to support those claims). Elements of this approach that have been applied in a nongame setting are shown and ideas are discussed for applying the approach to an existing immersive game setting. Finally, the report offers suggestions for extending and applying this approach for existing games and the design of new ones.