The paper focuses on a research project which aims at understanding how tutors learn to grade the coursework of university students, which has always received little attention in the study of quality assurance procedures. Think-aloud protocols and semi-structured interviews to 25 lecturers of three different universities provided data to develop a new metaphorical framework for the understanding of tutor learning. Analyzing data from a socio-cultural perspective, it emerges how professional learning is an interplay between public knowledge and the teachers’ experience and wisdom and it is suggested that grading, feedback, second marking, and moderation are wonderful opportunities to develop a better understanding of teachers’ professional learning.