Plant genetic engineering is considered a potential approach to reduce costs for biofuel production from lignocellulosic material. However, the ability to control cell-wall composition without compromising plant performance is a key objective of bioenergy crop improvement. Plants have been engineered for the production of enzymes within the crop biomass, with an aim to minimize the costs of catalyst production in bioreactors. Future research on the upregulation of cellulose and hemicellulose biosynthesis pathway enzymes for an increase in polysaccharides may also have the potential to improve cellulosic feedstocks. The most successful efforts to date have focused on the modification of lignin quantity and/or quality, in an effort to obviate the need for expensive pretreatment processes. Here we report a method for rapid detection of improved biodegradability in genetically modified plants that vary in lignin content and/or composition. For this purpose, only 50 mg of ground material is needed for liquid hot water pretreatment, and the method allows the pretreatment of up to 9 samples every 10 min per sandbath. Enzyme hydrolysis in the presence of commercial cellulases and β-glucosidase is performed in a final volume of 1 mL for 30 min, at 50 °C, and pH 4.8. The samples are then centrifuged, and the amount of glucose liberated is analyzed via a microplate assay. Using this approach, we have been able to rapidly and reproducibly identify genetically modified plants with improved biodegradability.