A two-step procedure involving a dilute-acid presoaking step and an aqueous-ethanol organosolv treatment has been evaluated and optimized for the conversion of Miscanthus x giganteus (MxG). This process allowed for the efficient fractionation of the raw material into a cellulose-rich residue, ail ethanol organosolv lignin fraction, and a water-soluble fraction mainly containing hemicellulose sugars. It was found that the presoaking step not only allowed a better recovery of xylans, but also enhanced the dissolution of lignin in the aqueous ethanol and the digestibility of the remaining cellulose by enzymes. The optimized conditions yielded a solid residue containing about 95% of the initial glucans, from which 98% was recovered after 48 h of enzymatic hydrolysis. In addition, 71% of the lignin was recovered as ethanol organosolv lignin (EOL), and the recovery of the xylans was equivalent to 73% of the xylose present in the raw Miscanthus.