This exploratory study investigates how successfully advanced Generation 1.5 college writers can revise their grammar errors in out-of-class writing when a specific set of grading symbols is used and grammar addressing these same points is being taught. While recent research on Generation 1.5 writers’ error correction using data from in-class writing gives insight into their ability to self-edit (Ferris, 1997; Ferris & Roberts, 2001), it does not address the more demanding task of revising an out-of-class analytical paper. The study involved comparing an early draft (with errors indicated in various ways) and the final draft of an analytical paper of 58 Generation 1.5 students in an advanced ESL composition class to determine their success in correcting eight of their most frequent and problematic grammar errors. The average success rate for all untreated errors was 32% versus a success rate ranging 77-81% for errors treated in some way, indicating a marked disparity in correction success between marked and unmarked errors. The study also shows conditional and word-choice errors are the most difficult of the errors studied for these students to correct. Implications of the findings for error treatment and grammar instruction are discussed.