The purpose of this study was to compare the effectiveness of two types of historical problem-solving instruction with advanced urban high school students' (N = 231) ability to reason with and contextualize historical evidence. Contextualization is a critical heuristic in the process of disciplinary thinking among historians. Yet, prior research shows students face significant challenges when contextualizing information (Reisman and Wineburg in Soc Stud 99:202-207, 2008; van Boxtel and van Drie in Cognit Instr 30:113-145, 2012). Seven teachers who collectively taught 14 sections of social studies were randomly assigned to explicit instruction in sourcing, contextualization and corroboration (a) that emphasized the role of individual cognition or (b) the same explicit instruction plus small group and whole class discussion. Students were administered pretests on relevant content knowledge and a historical writing task. After a one-week intervention, students completed a parallel writing task and a second reasoning task that required short written responses. After controlling for teacher and pretest scores, the findings indicated that students who were taught the cognitive approach scored higher on historical writing (ES = 0.33). Further analysis revealed they included greater contextualized thinking (ES = 0.44) and use of evidence (ES = 0.32) in post-intervention essays; in contrast, sourcing scores were comparable. Students in both groups performed equally well on the second reasoning task. Findings highlight the importance of teaching writing explicitly as part of history instruction and the role of cognition to enhance learning.