Research on impact of sustained impromptu speaking on public speaking competency development is scarce and lacking. The researcher investigated Moroccan college students' public speaking competency development through extemporaneous (i.e. carefully prepared and rehearsed) speech performance, after implementation of a teaching strategy involving treatment through weekly impromptu (i.e., involving little or no preparation) speaking sessions combined with individual goal-setting strategy (teacher feedback). For this purpose, the researcher assessed 64 extemporaneous speeches delivered over the course of a semester using the public speaking competence rubric (PSCR), and observed the students' public speaking progress through 90 impromptu speaking activities using a weekly goal-setting strategy. Results revealed that a combination of sustained impromptu speaking and goal-setting contributed significantly and effectively to public speaking skills development over the course of the semester. They also clearly showed that the teacher's weekly goal-setting strategy played a major role in building speakers' confidence and overall improvement. Considering the linguistic and cultural background of the students involved, together with the speech genres and the instructor's task requirements, new public speaking competency dimensions and sub-dimensions have been identified.