The impact on support services for persons with intellectual and developmental disabilities of the socioeconomic movements and theoretical reformulations of the last decades has generated the necessity, in order to guarantee their sustainability, to carry out processes of profound change in their organizational culture, intervening in the elements that compose it. Among them are professional practices as the best way to intervene in culture, with the use of comparative analysis between an organization's current practices and those expected with culture change. In this line, the organizational self-assessment tool "Organizational Effectiveness and Effi-ciency Scale" (OEES) is applied in a study with 24 organizations, which uses a collaborative assessment approach in the service of a set of evidence-based practices identified as standards in key aspects that guide culture change, specifically, a person-centered approach, participative structures, use of information systems and data man-agement, implementation of quality systems and participative and transformational leadership. The results ob-tained show that a large majority of organizations have significant discrepancies between their current practices and evidence-based practices. The descriptive analysis allows affirming the usefulness of the scale for an orga-nizational diagnosis and identification of strategies to guide transformational change.