Despite a long debate and the accompanying call for changes in the past few decades, grammar instruction in college English classes, according to some scholars, has remained largely "disempowering,""decontextualized," and "remedial" (Micciche, 2004, p. 718). To search for more effective and empowering grammar teaching, this study explores the use of corpora for problem-based learning/teaching of lexicogrammar in a college English grammar course. This pedagogy was motivated by research findings that (1) corpora are a very useful source and tool for language research and for active discovery learning of second/foreign languages, and (2) problem-based learning (PBL) is an effective and motivating instructional approach. The data collected and analyzed include students' individual and group corpus research projects, reflection papers on corpus use, and responses to a post-study survey consisting of both open-ended and Likert questions. The analysis of the data found the following four themes in students' use of, and reflections about, corpus study: (1) critical understanding about lexicogrammatical and broader language use issues, (2) awareness of the dynamic nature of language, (3) appreciation for the context/register-appropriate use of lexicogrammar, and (4) grasping of the nuances of lexicogrammatical usages. The paper also discusses the challenges involved in incorporating corpus use into English classes and offers suggestions for further research. (Contains 1 table, 1 figure, and 6 notes.)