It is the thesis of this discussion that outcome-based instructional systems (such as mastery learning, individually guided education, and competency-based education) represent a workable alternative to traditional approaches to instruction and are particularly suited to children in Head Start and Follow Through programs. This thesis is expanded mainly through a brief description of the elements of mastery learning and through discussions of organizational dimensions and the operational character of outcome-based practice. After describing the development of a researcher/practitioner coalition addressing implementation obstacles, discussion of organizational dimensions focuses on major obstacles to implementing mastery learning and philosophical premises underlying outcome-based practice. Specifically explored are staff attitudes and beliefs, role responsibilities and techniques, and organizational structure and procedure. Operational character is discussed in terms of learning outcome goals, criterion-referenced assessment and reporting, curriculum, instructional process, information management, success-oriented record keeping, and program evaluation. In general, the examination concerns philosophical premises, optimal instructional conditions, and operational components of outcome-based practice and suggests how these factors are related to apparent attitudinal, role performance, and structural obstacles to implementation. Concluding remarks concern how such factors are related to obstacles posed by the system of power and incentives governing school operations. Implications for Project Follow Through are pointed out. (RH)