How do you know if your lecture is hitting the right notes? Are any students struggling with the pace, complexity or amount of material in your presentation? Many of us will rely on puzzled facial expressions or signs of disinterest to infer student engagement level, but is there a better way? I will share my experience tackling such questions in large group teaching sessions. I designed a short and simple anonymous Mentimeter feedback form that can be completed by students in a matter of seconds at the end of any lecture. Following testing this approach during two of my face-to-face lectures attended by approximately 80-120 first year students, I will discuss the overall response and any ideas for adapting this strategy in the future. It may need to be used sparingly to avoid survey fatigue, but it has promising potential for quickly identifying ways to improve the content and accessibility of new lectures.