The diffusive behavior of membrane proteins has been reported to change with the timescale of the measurement. High-speed single-particle tracking studies have revealed that it is Brownian on time scales less than 100 μs, confined from 1 to 10 ms, and Brownian at longer times (>10 ms).1 This behavior has been interpreted as hop diffusion between submicron compartments in the plasma membrane. Due to the fundamental difficulty in achieving simultaneously high spatial and temporal resolution, these results have relied on a single experimental approach. Furthermore, attempts to use a complementary fluorescence technique to study anomalous diffusion have not reproduced the hop diffusion model.2Here we use interferometric scattering microscopy (iSCAT)3 to track the motion of the GM1 ganglioside receptor binding the B subunit of cholera toxin using 40-nm gold nanoparticle labels, in both supported lipid bilayers (SLBs) and droplet hydrogel bilayers (DHBs).4 In SLBs, in single trajectories containing >200,000 frames and providing simultaneous 10 μs temporal and sub-nm spatial precision, we observe a shift from Brownian diffusion at early time scales (30 - 100 μs) to confined diffusion (100 μs - 10 ms) back to Brownian diffusion (>10 ms). In contrast, GM1 diffusion in DHBs is Brownian at all timescales. These data suggest that the presence of a structural support on one side of the bilayer is sufficient to produce anomalous diffusion, even for diffusers that do not penetrate the membrane.1. Kusumi, A. et al. Annu. Rev. Biophys. Biomol. Struct.34, 351-378 (2005).2. Weiser, S. et al. Biophys. J. 92, 3719-3728 (2007).3. Ortega-Arroyo, J. and Kukura, P. Phys. Chem. Chem. Phys. (2012)DOI: 10.1039/c2cp41013c4. Thompson, J. R et al.Nano Lett.7, 3875-3878 (2007).