In Wikipedia, volunteers collaboratively author encyclopedic entries, and therefore managing conflict is a key factor in group success. Behavioral research describes 3 conflict types: task-related, affective, and process. Affective and process conflicts have been consistently found to impede group performance; however, the effect of task conflict is inconsistent. We propose that these inconclusive results are due to underspecification of the task conflict construct, and focus on the transition phase where task-related disagreements escalate into affective and process conflict. We define these transitional phases as distinct constructs—task-affective and task-process conflict—and develop a theoretical model that explains how the various task-related conflict constructs, together with the composition of the wiki editor group, determine the quality of the collaboratively authored wiki article. Our empirical study of 96 Wikipedia articles involved multiple data-collection methods, including analysis of Wikipedia system logs, manual content analysis of articles' discussion pages, and a comprehensive assessment of articles' quality using the Delphi method. Our results show that when group members' disagreements—originally task related—escalate into personal attacks or hinge on procedure, these disagreements impede group performance. Implications for research and practice are discussed.