Researchers quantified microplastic types, concentrations, anatomical burdens, geographic distribution and temporal differences in Pacific oysters and Pacific razor clams from 15 Oregon coast sites. Microplastics were present in organisms from all sites. Over 99% of microplastics were fibers. The material type was determined using Fourier-transform infrared spectroscopy. Spring samples contained more microplastics than summer samples in oysters but not razor clams. This study is the first to document microplastics in Pacific razor clams and provides important coast-wide data to compare microplastic burden across species, seasons, and sites.