This study explores the organizational nature of curricular leadership in middle schools. A conceptual model of the organizational structure and effects of curricular leadership in middle schools is presented. The Organizational Curricular Leadership (OCL) model suggests that the relationship between organizational inputs and effectiveness in middle schools is mediated by a variety of organizational curricular leadership (OCL) variables. Five meaningful dimensions of OCL are empirically derived. The OCL model posits multiple, reciprocal relationships occurring among school inputs, OCL variable dimensions, and school outcomes. OCL variable linkages to various indices of school effectiveness are posited and explored using quantitative methods. The model is operationally defined through the development of a new quantitative measure of overall OCL leadership in middle schools—the Organizational Curricular Leadership Inventory (OCLI). A variety of implications are derived from study findings for: (1) recasting and extending notions of conceptual-based research on middle school organizations; (2) informing curricular leadership in middle schools; and (3) guiding further middle school organizational curricular leadership and effectiveness studies.