BACKGROUND: For the last few years, English general practices - which are, traditionally, small - have been encouraged to serve larger populations of registered patients by merging or collaborating with each other. Meanwhile, patient surveys have suggested that continuity of care and access to care are worsening. AIM: To explore whether increasing the size of the practice population and working collaboratively are linked to changes in continuity of care or access to care. DESIGN AND SETTING: This observational study in English general practice used data on patient experience, practice size, and collaborative working. Data were drawn from the English GP Patient Survey, NHS Digital, and from a previous study. METHOD: The main outcome measures were the proportions of patients at practice level reporting positive experiences of both access and relationship continuity of care in the GP Patient Survey. Changes in proportions between 2013 and 2018 among practices that had grown and those that had, roughly, stayed the same size were compared, as were patients' experiences, categorised by whether or not practices were working in close collaborations in 2018. RESULTS: Practices that had grown in population size had a greater fall in continuity of care (by 6.6%, 95% confidence interval = 4.3% to 8.9%), than practices that had roughly stayed the same size, after controlling for other factors. Differences in falls in access to care were smaller (4.3% difference for being able to get through easily on the telephone; 1.5% for being able to get an appointment; 0.9% in satisfaction with opening hours), but were statistically significant. Practices collaborating closely with others had marginally worse continuity of care than those not working in collaboration, and no differences in access. CONCLUSION: Larger general practice size in England may be associated with slightly poorer continuity of care and may not improve patient access. Close collaborative working did not have any demonstrable effect on patient experience.