This report is a 20-month longitudinal investigation of six international teaching assistants newly arrived in the U.S. and their spoken English fluency and prosody. The goal was to create a developmental account of ITAs' growth against the backdrop of key institutionally-determined events in ITAs' careers: Language-focused interventions, teaching-focused interventions, and teaching assignments. A second goal is to consider the roles of explicit and procedural knowledge in second language fluency and prosody growth, with consideration to ITAs' L1s and their spoken L2 ability upon arrival at an institution. Both of these variables, and ITAs' career experiences (interventions, teaching assignments, etc.), are linked. There were four data collections in which participants did two parallel tasks based on short texts from their academic areas: Reading a passage aloud from a text, and presenting on the passage topic. The results showed that ITAs held steady or improved their spoken speech rates, but not necessarily their ability to speak in complete idea units. Some ITAs improved on the prosody measures, but others did not, particularly on the presentation task, suggesting a sustained sensitivity of ITAs' talk to task demands. Ratings on ITA comprehensibility from undergraduates generally reflected shifts in ITAs' fluency and prosody. The results propose an important implication: When learners no longer have the benefit of language-focused instruction, and their explicit knowledge of fluency and prosody features is no longer salient, does this shut down a path to proceduralization?