Second language (L2) researchers and teachers have increasingly come to believe that using a computer-based corpus can be extremely helpful in the language classroom. The purpose of this study is to examine whether corpora can be used outside of the classroom in order for students to improve their essays independently. No previous study has tried to examine students' essays in relation to corpus use so that this study is exploratory. Seven international students wrote five essays on specific topics and then corrected their errors through corpus research. Two experiments were conducted with different students and followed three steps: receiving information about how to use the BYU COCA, writing and correcting, and interviews with students. I examined quantitatively the number and types of errors that students were able to correct in two experiments and reported qualitatively on students' interview responses.