Background There are substantial concerns about GP workload. The Quality and Outcomes Framework (QOF) has been perceived by both professionals and patients as bureaucratic, but the full impact of the QOF on GP workload is not well known. Aim To assess the impact of the QOF on GP consultation rates for patients with diabetes mellitus. Design and setting This study used interrupted time series of 13 248 745 general practice consultations for 37 065 patients with diabetes mellitus in England. Method Clinical Practice Research Datalink general practice data were used from 2000/2001 to 2014/2015, with introduction of the QOF (1 April 2004) as the intervention, and mean annual GP consultation rates as the primary outcome. Results Mean annual GP clinical consultation rates were 8.10 per patient in 2000/2001, 6.91 in 2004/2005, and 7.09 in 2014/2015. Introduction of the QOF was associated with an annual change in the trend of GP clinical consultation rates of 0.46 (95% confidence interval [CI] = 0.23 to 0.69, P = 0.001) consultations per patient, giving a post-QOF trend increasing by 0.018 consultations per year. Introduction of the QOF was associated with an immediate stepped increase of 'other' out-of-hours and non-clinical encounters, and trend change of 0.57 (95% CI = 0.34 to 0.81, P<0.001) per year, resulting in a post-QOF trend increasing by 0.27 other encounters per year. Conclusion Introduction of the QOF was associated with a modest increase in clinical GP consultation rates and substantial increase in other encounters for patients with diabetes independent of changes in diabetes prevalence. National prevalence of diabetes increased by 90.7% from 2004/2005 to 2014/2015, which, combined with this study's findings, means GPs would have provided nearly double the number of consultations for patients with diabetes over this timescale.