This longitudinal case study investigated the developmental trajectories of two participants enrolled in an ITA oral communication course at Purdue University. The course provides language support to the ITA population who play a crucial role in higher education programs in the U.S. (Gorsuch, 2016). Over four months (i.e., one semester), I collected speech data from participants' responses to different tasks across 14 weeks and surveyed their weekly practice and goals. The multi-dimensional construct of L2 oral proficiency was assessed by eight large- and fine-grained variables representing various subdimensions of fluency, complexity, and accuracy (CAF, Skehan, 1998), including speed fluency (Articulation Rate & Mean Length of Run), breakdown fluency (Mid-unit Silent Pause Duration & Filled Pause Rate), repair fluency (Repair Rate), syntactic complexity (Mean Length of AS-unit), lexical diversity (vocd-D), and accuracy (Error Rate). Dynamic Systems Theory (DST) methods were employed to visualize trends over time (Lowess trend lines, moving min-max graphs), and correlation analyses (Kendall's Tau for small sample size and moving correlations) were performed to examine both general and local interactions between CAF dimensions and subdimensions. Results showed noticeable improvement in the L2 oral proficiency of both participants, though the extent of progress varied. Andy, an intermediate learner, improved in breakdown/ repair fluency and accuracy, but not in speed and syntactic/lexical complexity. Zach, an intermediate-to-advanced learner, demonstrated progress in almost all CAF subdimensions except for repair fluency. Several noteworthy findings emerged from the study. First, both participants made noticeable gains in accuracy, which can be attributed to formal instruction. Second, the participants exhibited stabilization or regression in speed instead of progress, which may be a strategic allocation of attention and linguistic resources towards more important aspects such as smoothness (represented by mean length of run, (Lennon, 1990)) and accuracy. Thirdly, gains in complexity were observed only in the more advanced learner, suggesting a potential sequence of acquisition. Improving syntactic and lexical complexity may require a certain level of oral proficiency mastery, and both may be compromised in productions by lower-level students like Andy, whose lexical diversity even decreased over time. Fourthly, observed gains aligned well with semester goals and weekly practices, highlighting the importance of goal setting and practices in language learning. Lastly, more significant correlations between CAF subdimensions were observed in Andy, supporting the limited attentional capacity hypothesis (Skehan, 2014). Additionally, dynamics relationships between CAF were observed for the participants, both in strength and direction. Interestingly, Andy's shift in the relationship between accuracy and speed fluency from competitive to supportive, indicating development. The study is the first attempt to investigate the development of all CAF dimensions from a DST perspective within the context of an ITA program. As an exploratory endeavor, it offers valuable and detailed insights into the L2 speech learning process of two learners within a particular, local setting. These findings have implications for larger-scale group studies in the field of L2 acquisition, as well as for classroom teaching, assessment, and program evaluation within ITA support programs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]