Pedagogical activities that combine mobility, collaboration and game mechanics present significant advantages to attract students’ attention and maintain their engagement in learning. Teachers naturally try to combine mobility and collaboration when they create field trips. Indeed, they identify several Points Of Interest that learners physically need to go to, thus requiring mobility, and they usually group students in teams to encourage collaboration, even if such collaboration is seldom attained. However, using the third element - game mechanics - is harder for teachers because they are not familiar with game models and often not gamers themselves. In this article, we present the MOCOGA Model, a MObile COllaborative learning GAme Model that is designed to adapt to many types of field trips. This model also offers a nested design approach that guides teachers in enriching their field trips iteratively. This model is the first step towards the development of an authoring tool that will enable teachers to create their own smartphone applications.