This chapter reviews themes in research into the effectiveness of oral corrective feedback, typically provided by language teachers, on L2 grammatical development. It synthesizes research evidence for the effects of oral corrective feedback on learners’ development of grammar and the relative efficacy of different corrective feedback strategies, such as output-prompting and input-providing. Further themes concern the effectiveness of oral corrective feedback on salient and non-salient grammatical features and in relation to learners’ varying levels of knowledge of the targeted features. Even though most research in this area concerns the development of accuracy, the chapter includes a review of the considerably smaller body of literature that offers insights into the potential value of oral corrective feedback on the development of fluency. The chapter reviews the different kinds of oral and written tests that have been used in research to gauge grammar learning, some of which teachers may wish to consider adopting to assess their learners. Based on the cumulative evidence from research, we make suggestions for classroom teachers, although we recognize that teachers’ decisions about the provision of oral corrective feedback are often based on multiple factors, including affective factors and teaching objectives.