BACKGROUND: Health care systems globally are facing challenges of meeting the growing demand for primary care services due to a shortage of primary care physicians. Policy makers and administrators are searching for solutions to increase the primary care capacity. The effective utilization of nurse practitioners (NPs) has been proposed as a solution. However, organizations utilize NPs in variable capacities. In some settings, NPs serve as primary care providers delivering ongoing continuous care to their patients, referred to as patient panels, whereas in other settings they deliver episodic care. Little is known about why organizations deploy NPs differently. OBJECTIVES: Investigate the NP role in care delivery-primary care providers with the own patient panels or delivering episodic care-within their organizations and understand how work environments affect their role. DESIGN: A cross-sectional survey design was used to collect data from primary care NPs. SETTINGS: The study was conducted in one state in the United States (Massachusetts). Data from 163 primary care organizations was obtained, which employed between one to 12 NPs. PARTICIPANTS: 807 NPs recruited from the Massachusetts Provider Database received mail surveys; 314 completed and returned the survey, yielding a response rate of 40%. METHODS: The survey contained measures of NP role in care delivery and work environment. NP role was measured by an item asking NPs to report if they deliver ongoing continuous care to their patient panel or if they do not have patient panel. The work environment was measured with the Nurse Practitioner Primary Care Organizational Climate Questionnaire (NP-PCOCQ). The multilevel Cox regression models investigated the influence of organization-level work environment on NP role in care delivery. RESULTS: About 45% of NPs served as primary care providers with their own patient panel. Organization-level Independent Practice and Support subscale, an NP-PCOCQ subscale, had a significant positive effect on NP role (risk ratio=2.33; 95% CI: 1.06-5.13); with a one unit increase on this subscale, the incidence of the NPs serving as primary care providers with their own patient panel doubled. CONCLUSIONS: NPs can help meet the increasing demand for primary care by taking responsibilities as primary care providers, and organizations can assign NPs their own patient panels. Supporting NP independent practice within organizations promotes NP role as primary care providers. Policy and organizational change focused on promoting NP work environments so NPs can practice as primary care providers can be an effective strategy to increase the primary care capacity.