Augmented Reality Game-Based Learning (ARGBL) is becoming increasingly relevant in Technology-Enhanced Learning. Games with AR characteristics, or even AR applications structured with rules and game elements, are proving to be effective and successful learning experiences. There is a need to include teachers in the design process. In this paper, two case studies are shown in order to validate a methodological approach for the co-design of ARGBL, in which 6 teachers participated. This is a co-design method that proposes a thorough, iterative process guided by design principles and mediated by dialogue among the stakeholders. Here, the process of co-design with teachers is analyzed and assessed using mixed-methods observations on the use of the produced ARGBL games with students on naturalistic environments. The validation process links the usefulness of the ensuing products with the use of the method and shows the benefits of using co-design methods to create ARGBL experiences.