This paper presents a series of experiments that tested the usefulness of teaching Spanish mood using an approach to Cognitive Grammar specifically developed for the foreign language classroom: "Operational Grammar." Mood selection is one of the most difficult aspects of learning Spanish as a FL, and it is one of the last features acquired. It is unquestionably complex, involving issues of subordination, alternation, and speaker's communicative intent. This complexity has been amplified by the traditional approach to mood, which has changed little over the last 50 years. The alternative presented here sees language as a symbolic representation of the speaker's mental model of the world. Grammar is closely linked to this model as the tool used in class to help learners communicate meaning through form. This enables them to understand how native speakers choose to communicate. Language, then, portrays an outcome of the speaker's own selection, guided by communicative intent and not as part of a taxonomic set of rules. The empirical study showed that the combination of a cognitive approach to mood with a Processing Instruction methodology had positive effects on how the students identified mood selection in both input and output learning situations. (Contains 5 tables, 9 figures, and 16 notes.)