This paper presents the results of a study investigating the impact of interactional feedback on interlanguage variation in terms of accuracy, complexity, and fluency of learners' discourse in performing tasks with familiar vs. unfamiliar topics. The participant of the study who were randomly assigned into an experimental and a control group were required to perform a task with a familiar topic and one with an unfamiliar topic. The experimental group received interactional feedback while performing both tasks. The results revealed that the participants exposed to interactional feedback while performing both tasks achieved greater accuracy and complexity, but lower fluency. Greatest fluency was achieved by the participants who benefited from topic familiarity and were not interrupted with feedback moves. The findings highlight the need to consider interactional feedback as a task implementation condition in task grading and sequencing in syllabus design and materials development. (Contains 6 tables and 3 figures.)