OBJECTIVES: In 2022, England embarked on an ambitious reorganisation to produce an integrated health and care system, intended also to maximise population health. The newly created integrated care systems (ICSs) aim to improve quality of care, by achieving the best outcomes for individuals and populations through the provision of evidence-based services. An emerging approach for managing quality in organisations is the Quality Management System (QMS) framework. Using the framework, this study assessed how ICSs are managing and improving quality. METHODS: Four ICSs were purposively sampled, with the data collected between November 2021 and May 2022. Semi-structured interviews with system leaders (n=60) from health and social care, public health and local representatives were held. We also observed key ICS meetings and reviewed relevant documents. A thematic framework approach based on the QMS framework was used to analyse the data. RESULTS: The ICSs placed an emphasis on population health, reducing inequity and improving access. This represents a shift in focus from the traditional clinical approach to quality. There were tensions between quality assurance and improvement, with concerns that a narrow focus on assurance would impede ICSs from addressing broader quality issues, such as tackling inequalities and unwarranted variation in care and outcomes. Partnerships, a key enabler for integration, was seen as integral to achieving improvements in quality. Overall, the ICSs expressed concerns that any progress made in quality development and in improving population health would be tempered by unprecedented system pressures. CONCLUSION: It is unclear whether ICSs can achieve their ambition. As they move away from an assurance-dominated model of quality to one that emphasises openness, learning and improvement, they must simultaneously build the digital infrastructure, staff expertise and culture to support such a shift.