The city of Rio de Janeiro has implemented, on a large scale, the model of Social Organizations (OSS) for the management of Primary Health Care (PHC). This option makes the understanding of the city's experience very relevant, especially since, until then, the OSS organizational model had been adopted predominantly in the SUS hospital management. Thus, the experience of PHC development at two conflicting moments of municipal management in relation to the OSS model is analyzed: the implementation and development of the PPPs (2009-2016); and their dismantling (2017-2020). Case Studies, Literature Review and analysis of public data from DATASUS/Ministry of Health were used. It was verified that: the adoption of outsourcing based on OSS can be directly associated with the rapid expansion of PHC in the city and PHC coverage improvement indicators; the diffusion of the OSS model is associated with the high priority given to health expenditures in the municipal budget; the sustainability of the adoption of the OSS model did not depend on the municipality's economic status, but on the government's political choice in the period of 2009 to 2016. The PPP arrangement resulted in important organizational advances, although it did not prevent the veto of the OSS model carried out during the 2017-2020 term