Autonomous work groups are involved in goal setting and planning and hence can define their jobs and the outcome idiosyncratically. Our interest lies in how job design restricts or creates possibilities for groups to redefine their work and thus go beyond formal requirements. The aim was to test a model of the relationships between dimensions of job design, group processes, group initiative, and self-organizational activities. The results are based on work task analyses and questionnaires administered to 31 work groups at four Swedish industrial companies. The theoretical input-process-output model received substantial support. Dimensions of job design affect whether a group, through collective reflexivity, can redefine work and proactively create conditions and organize work so that uncertainty can be handled and new tasks mastered. Group processes such as cooperation and social support enhance group initiative to achieve such meaningful change. In this study, reflexivity does not impact on group initiative, but does explain the major amount of variance in self-organizational activities. Work task analyses can be a useful tool for providing groups with the prerequisites for self-organizational activities. We believe these to be essential for the groups' capacity to be involved in the innovation process from idea to finished product.