This inquiry explored the degree to which first language (L1) fluency behavior, cross-linguistic differences, and competence can predict second language (L2) fluency behavior over time. English L1 Spanish (n = 24) and French (n = 25) majors completed a picture-based oral narrative in the L2 before and after 5 months residing abroad and later in the L1 after returning home. Data were coded for seven measures of speed, breakdown, and repair fluency. The results from multiple regressions pointed out that L1 fluency behavior, cross-linguistic differences, and competence differentially contributed to clarifying L2 fluency behavior previous to and during immersion. These findings propose that when exploring L1–L2 fluency relationships considerations of moderating factors like cross-linguistic differences are necessary, and it is worthwhile to center on how the contributions of these factors shift during evolution.