Extensive research supports the claim that student-instructor interaction is an essential element of successful online teaching. It is less clear, however, whether teaching presence is discipline-specific, or how it may be affected by the personal and professional background of individual instructors. This article describes the quantitative portion of a mixed methods study to analyze patterns of commenting behaviours in a graduate-level, online nursing course. Following the Community of Inquiry theoretical framework (Garrison, Anderson & Archer, 2000), we compare experienced and inexperienced instructors, and specifically focus on how teaching presence evolved over a fifteen-week course. Our findings indicate that teaching experience affects the types and density (number per post) of comments used by teachers. Experience played a role in how density and overall level of activity evolved as the semester progressed. No differences in teaching presence emerged when comparing instructions for each assignment, but there were differences when comparing instructions to teacher posts. [The publication year on the pdf is incorrect, the correct year is 2022.]