Situated learning theories such as communities of practice provide a rich conceptual framework for analyzing the processes by which newcomers become full participants in the communities they enter. However, some research shows that these concepts have shortcomings for theorizing learning in formal educational settings especially when it comes to adult academic and career preparation. To redress these problems, we propose the conceptual framework of "quasi-communities," which retains some of the dimensions of the original concept while abandoning others. We use a case study of the continuing training of mariners as evidence to show how this framework is developed to identify and eventually improve learning in formal adult and vocational education. Our analysis illustrates the variable learning opportunities in these settings that are available or might be developed within this framework.