Teacher telling is underrepresented in the mathematics education reform literature and deserves additional scrutiny. This case study examined a skilled teacher's telling practices during a university mathematics content course for pre-service elementary teachers. I identified telling practices through discourse analysis, attending to the presence of mathematics and the contribution of new structure or ideas from the teacher. The teacher utilized seven unique types of mathematical telling while supporting collaborative group work on tasks. The study identified subtle telling, implicit telling, and explicit telling. The results suggest that mathematical telling is an integral part of the teacher's role in inquiry-based instruction and should not be overlooked. Researchers can use the telling types to identify and describe telling practices more transparently. Practitioners can more consciously incorporate and discriminate between telling practices.