The properties of InAs quantum dots (QDs) deposited on compositionally homogenous and laterally modulated surfaces is investigated by photoluminescence (PL), atomic force microscopy (AFM), and transmission electron microscopy. We use solid source molecular beam epitaxy on (100)-oriented InP substrates to fabricate the samples. It is found that QDs grown on a laterally modulated surface are more uniform in size. This is implied by a decrease of 22% in the full width at half maximum (FWHM) in the PL signal at 77 K for InAs QDs deposited on the modulated surface as opposed to the homogenous surface for equal monolayer coverage of InAs. Similarly, plan view scans taken by ex situ contact AFM also show improved size uniformity of QDs grown on the laterally composition modulated surface as evidenced by a decrease in the standard deviation of area data compiled from the images. It is shown that the improvement in the geometrical uniformity of the quantum dots as depicted by the PL FWHM and AFM data is facilitated by an early onset of size self-equalization due to the lateral composition modulation.