Guided by the Second Language Motivational Self System (L2MSS) framework, this study examined to what extent the L2MSS components of ideal self, ought-to self, and learning experience described the motivation of learners who chose to enroll in college elective courses of modern languages other than English (LOTEs) in the monolingual social setting of Taiwan. Questionnaire surveys were conducted at the end of two consecutive semesters and learners were interviewed. Triangulation of survey and interview data suggested that a positive learning experience was the strongest variable in motivating effort. Although some classroom factors were known, others worth further exploration in instructional settings were pointed out. The ought-to L2 self was found to be an insignificant predictor with questionable validity. Instead, academic responsibility and instrumentality were found to be more relevant factors. Results on ideal self were less straightforward, suggesting that the ideal self for LOTEs may be qualitatively different from the English ideal self. Comparisons of data sets across time and learner groups indicated motivation did not change over time. By considering major L2MSS components and related constructs together, this study uncovered their relative adequacy in explaining LOTE motivation and suggested possible new perspectives for studying LOTE motivation in instructional settings.