The examples used in the teaching-learning process of mathematics have a crucial role in fostering conceptual understanding, and some variables can affect instructors' qualified example usage. This longterm study focused on mathematics teachers' exemplification process in face-to-face and online learning environments. In this regard, the change in examples used by mathematics teachers were evaluated in terms of content preparation and presentation during the shift from face-to-face lectures to online classes. A longitudinal design was used in the study and the teaching processes of 14 middle-school mathematics teachers were observed over two semesters. Observation notes, course documents, and semi-structured interview data were analyzed, and content analysis findings were presented through descriptive statistics in order to compare content preferences in two different learning environments. The use of worked examples decreased, while the use of conceptual examples increased with the shift from face-to-face lectures to online classes. Also the length of time devoted to examples in online classes decreased, and examples were more teacher-centered. The interview revealed that mathematics teachers need support in terms of example preparation and presentation aspects in online learning environments. The other technological-pedagogical competencies that teachers might need to choose qualified examples in different teaching-learning environments are discussed in the light of relevant literature.