Methodology of the research that will be presented, is based on the life-long learning conception, learning organization conception (Senge, 1990, Pedler, 1991) and its derivative - personal mastery (Senge, 1990), Action Science conception ( Argyris&Schon) and social exchange theory as a basis for learning-in-partnership networks. The object of the research is the model of competence development within the school (institution). The research theoretical approach, empirical base and methods. Lithuanian context, Lithuanian education reform and teachers' professional development require data reflecting the reality of post-soviet country experiencing fast and essential changes - gap of Lithuanian schools or equivalent achievements when analyzing similar organizations development tendencies on a world scale, teachers' competence development in an organization, etc. Fixed deficiency of such knowledge forms the problem of the research. The purpose of the research is to theoretically found the institutional teacher's competence development model and to define empirically its implementation preconditions in Lithuania (post-soviet country experiencing fast and essential changes). The article theoretically grounds the institutional teacher's competence development model, combining three parts: Teachers' Action Research, Compiling (cumulating) Teacher's Competence Portfolio and Learning in Partnership Networks within the Institution. Specific methods, action means and necessary abilities are analyzed. Method - scientific literature and secondary source analysis. Respondents' opinion collected by survey method will help to examine school's context, i.e. preconditions for teachers' competence development inside institution: teachers' view to action, research, Compiling (cumulating) portfolio of competence, and Learning in Partnership Networks. Questioning is being carried out, 300 questionnaires are distributed. Results of the research and their exhaustive interpretation will allow improving teachers' professional competence development ways and improving institution's - school's activity. Tendencies revealed in Lithuanian context could be valuable to education researchers and politicians, teachers and teachers' continuing education organizers, heads of educational institutions and active educators from countries with different experience and history.