A complete understanding of the complexities of charge transport through disordered organic materials is needed in order to advance organic electronics technology. Even relatively crystalline films can exhibit local variations in electrostatic potential due to charge traps (structural defects, chemical impurities, dynamical disorder, etc) which inhibit efficient transport [1]. We have studied local electrostatic potential variations in crystalline films of the organic compound difluoro-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) [2]. This solution processable small-molecule has shown good field effect mobilities [2]. Grazing Incidence Wide-Angle X-ray Scattering measurements show that films grown by organic molecular beam deposition onto a silicon dioxide substrate show a uniform (001) crystallite orientation, unlike solution-cast films that are a mixture of (001) and (111) crystallites [3]. Despite this uniform crystal orientation, our Kelvin Probe Force Microscopy (KPFM) studies show large variations (of more than 0.1 V) in the surface potential measured on separated crystalline domains. Furthermore, these variations in surface potential are shown to be influenced by a gate voltage applied to the dielectric. We attribute these variations to strong spatial inhomogeneity in the local trap density in the dif-TES-ADT films. The variations occur on the length scale of several hundred nanometers in polycrystalline, but well-oriented films. This mesoscale inhomogeneity needs to be modeled and controlled to optimize device performance. [1]Willa et al., J. Appl. Phys. 113, 133707 (2013). [2]Gundlach et al., Nat. Mater. 7, 216 (2008). [3]Li et al., Adv. Mater. 24, 5553 (2012).