CBAL (Cognitively Based Assessment of, for, and as Learning) is a research initiative intended to create a model for an innovative K-12 assessment system that documents what students have achieved ("of learning"); helps identify how to plan instruction ("for learning"); and is considered by students and teachers to be a worthwhile educational experience in and of itself ("as learning"). Because CBAL intends to not only measure student achievement but also facilitate it, CBAL, like any similar assessment program, requires a theory of action. This paper describes the notion of theory of action, offers a preliminary version of such a theory for CBAL, and outlines a provisional research program for evaluating that theory. (Contains 7 figures and 2 footnotes.)