Drawing upon contemporary research, this paper examines whether there is a relationship of STEM (science, technology, engineering and maths) bachelor and master graduates to the gender pay gap (GPG) in the 27 EU Member states in 2013-2020 using a novel cross-sectional data set based on the 2013 International Standard Classification of Education (ISCED). International panel data were analysed with the dynamic modelling fixed effects method and compared with the results received from the cross-sectional analysis executed with the help of Bayesian model averaging methods. Our findings suggest that STEM education plays a significant role in forming the GPG. We can see a negative, robust and statistically significant effect of bachelor- and master-level female STEM graduates on the GPG and a positive statistically significant effect of bachelor- and master-level male STEM graduates on the GPG. The permanently lower women-to-men ratio in STEM education and those employed in high-end sectors of science and technology can be one of the drivers of the persistent GPG in developed countries.