We present high spatial resolution observations of the continuum emission from the young multiple star system UZ Tau at frequencies from 6 to 340 GHz . To quantify the spatial variation of dust emission in the UZ Tau E circumbinary disk , the observed interferometric visibilities are modeled with a simple parametric prescription for the radial surface brightnesses at each frequency . We find evidence that the spectrum steepens with radius in the disk , manifested as a positive correlation between the observing frequency and the radius that encircles a fixed fraction of the emission ( R _ { eff } \propto \nu ^ { 0.34 \pm 0.08 } ) . The origins of this size–frequency relation are explored in the context of a theoretical framework for the growth and migration of disk solids . While that framework can reproduce a similar size–frequency relation , it predicts a steeper spectrum than is observed . Moreover , it comes closest to matching the data only on timescales much shorter ( \leq 1 Myr ) than the putative UZ Tau age ( \sim 2–3 Myr ) . These discrepancies are the direct consequences of the rapid radial drift rates predicted by models of dust evolution in a smooth gas disk . One way to mitigate that efficiency problem is to invoke small-scale gas pressure modulations that locally concentrate drifting solids . If such particle traps reach high continuum optical depths at 30–340 GHz with a \sim 30–60 % filling fraction in the inner disk ( r \lesssim 20 au ) , they can also explain the observed spatial gradient in the UZ Tau E disk spectrum .