Theories of action study what an actor do, in a given situation, in order to achieve consequence or objectives. Argyris and Schon made a distinction between espoused theories - those that an individual claims to follow - and theories-in-use - those that can be inferred from action -. In the software engineering field, software processes and practices constitute the espoused theory, since it is what engineers claim to follow. But what engineers - and especially apprentices - do may reveal a different theory-in-use. The capstone project provides students, working in groups, with the possibility to reflect on her/his action and that may help making explicit theories-in-use. The course of action theory considers the observable aspect of the actor's activity, i.e., what is presentable, accountable and commentable. The course-of-action observatory collects data on the courses-of-action. This observatory connects continuous observations and recordings of the agents' behavior, the provoked verbalizations of these agents in activity and the agents' comments in self confrontation with recordings of their behavior. A case study, based on the activity of a team of 6 young software engineer apprentices is used to illustrate the building and the data collecting of the course-of-action observatory and the self-reconstruction of apprentices' activity. As primary results of this work, we may think that self-observing and self-analyzing software engineer's activity help to reveal her/his theory-in-use - what governs engineers' behavior and tends to be tacit structures - and it may help them to learn more suitable theories-in-use, thus contributing to improve productivity and performance. In the special case of apprenticeship learning, it may form a part of an appropriate education intended to develop a reflective attitude.