Periphyton data consists of diatom scrubs sampled in a range of riffle and pool habitats including diatom taxa counts (identified to genus level) and computed autotrophic index (ratio of the organic mass per cm2 to mass (microgram) of chlorophyll a) as well as site characterisation data. The data were collected from the South Fork McKenzie river, Oregon, USA in September of 2021 and February 2022 following the Holiday Farm wildfire in Autumn 2020. Samples were collected from a restored and unrestored reach of the South Fork McKenzie River with a view to quantifying differences in periphyton response to wildfire in the restored vs. unrestored river reaches. The study was conducted by the University of Nottingham, with data collected by partners from The US Forest Service, Portland State University, Washington State University and Colorado State University. Funding for the work was received from the Natural Environment Research Council. Full details about this dataset can be found at https://doi.org/10.5285/6b7337fa-037b-4c03-a8be-fd4c5722fe1a