Introducing variability during learning often facilitates transfer to new contexts (i.e., generalization). The goal of the present study was to explore the concept of variability in an area of research where its effects have received little attention: learning through retrieval practice. In four experiments, we investigated whether retrieval practice with different examples of a concept promotes greater transfer than repeated retrieval practice with the same example. Participants watched video clips from a lecture about geological science and answered application questions about concepts: either the same question three times or three different questions. Experiments 3 and 4 also included conditions that involved repeatedly studying the information in the application questions (either the same example or three different examples). Two days later, participants took a final test with new application questions. All four experiments showed that variability during retrieval practice produced superior transfer of knowledge to new examples. Experiments 3 and 4 also showed a testing effect and a benefit from studying different examples. Overall, these findings suggest that repeatedly retrieving and applying knowledge to different examples is a powerful method for acquiring knowledge that will transfer to a variety of new contexts.