The efficacy of written corrective feedback (WCF) is affected by a variety of variables. To maximize the effect of WCF, it is necessary to find out what variables are more predictive of learning. The present study explored the best predictors of learning among six facets of WCF: explicitness, intensiveness, error type, complexity, languaging, and mode of languaging. Seventy-five first-year university students wrote an essay and received WCF on their errors. Then the essays with WCF were returned to learners, who were assigned to five conditions: languaging about WCF in written form prompted, languaging about WCF in written form unprompted, languaging in oral form prompted, languaging in oral form unprompted, and no languaging. The languaging groups languaged about the WCF they received and the non-languaging group only looked through the corrections on their essays. One day after the languaging activity, all groups took an immediate test, and 4 weeks later, a delayed test. It was found that learning in the immediate test was best predicted by error type, complexity, and languaging, and learning in the delayed test was best predicted by error type and mode of languaging. Based on these findings, the pedagogical implications of the study are discussed.