Background: Systems to detect and minimise unwarranted variation in clinician practice are crucial to ensure increasingly multidisciplinary healthcare workforces are supported to practice to their full potential. Such systems are limited in English general practice settings, with implications for the efficiency and safety of care. Aim: To evaluate the benefits and limitations of a continuous, risk-based, consultation peer-review system used for 10 years by an out-of-hours general practice service in Bristol, UK. Design and setting: A qualitative interview study in South-West England. Method: Semi-structured interviews with intervention users (clinicians, peer-reviewers and clinical management), analysed by inductive thematic analysis and integrated into a programme theory. Results: 20 clinicians were interviewed between September 2018 - January 2019. Interviewees indicated the intervention supported clinician learning through improved peer-feedback; highlighting learning needs and validating practice. It was compared favourably with existing structures of ensuring clinician competence; supporting standardisation of supervision, clinical governance and learning culture. These benefits were potentially limited by intervention factors such as differential feedback quality between clinician groups, the efficiency of methods to identify learning needs, and limitations of assessments based on written clinical notes. Contextual factors such as clinician experience, motivation and organisational learning culture influenced the perception of the intervention as a support or stressor. Conclusion: Our findings demonstrate the potential of this methodology to support clinicians in an increasingly multidisciplinary general practice workforce to efficiently and safely practice to their full potential. Our programme theory provides a theoretical basis to maximise its benefits and accommodate its potential limitations.