Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques were used to study the thermochemical behaviour of three varieties of oat straw (Sentinel, Shaw, and Tibor). The thermal degradation of oat straw was studied in an oxidizing atmosphere (15% oxygen and 85% nitrogen) from ambient temperature to a temperature of 700-degrees-C using a heating rate of 20-degrees-C min-1. Two distinct reaction zones were observed on the TGA and DTA curves. The kinetic parameters (order of reaction, activation energy, and pre-exponential factor) were determined for each zone separately by applying thermo-analytical techniques to the reaction kinetics. Higher thermal degradation rates were observed in the first reaction zone due to rapid release of volatiles as compared to those in the second reaction zone. The activation energies were in the range of 83-102 and 58-75 kJ mol-1 for the first and the second reaction zones, respectively.