In this work, the results of experimental studies on the pyrolysis of oat straw in a fixed-bed reactor at different temperatures are described. The pyrolysis products are analyzed, and the effect of the temperature on the product yield is also discussed. The bio-oil yield increased at low temperatures, while gas production was enhanced at high temperatures during oat straw pyrolysis. The highest percentage of bio-oil (40.5%) was produced at 450 °C, while the maximum gas production (42%) took place at the temperature of 550 °C. To evaluate the pyrolysis product yield, comparisons were made between the oat, wheat, and flax straws that were pyrolyzed in the lab under the same experimental conditions. A comparison of the biomasses based on the pyrolysis product yield illustrates that flax straw is capable of producing more hydrogen (33% of the outlet gas) and carbon-rich char (42% of the biomass) when compared to other biomasses. Oat straw is considered a better biomass for bio-oil production (46% of the vola...