Catalyzes the selective oxidation of C1 hydroxyl moieties on mono-, oligo- and polysaccharides with concomitant reduction of molecular oxygen to hydrogen peroxide. This results in the formation of the corresponding lactones, which typically undergo spontaneous hydrolysis. Xylooligosaccharide oxidase is able to oxidize a variety of substrates including D-xylose, D-cellobiose, lactose and arabinose. The enzyme acts primarily on xylooligosaccharides, indicating that it prefers pentose-based oligosaccharides over hexose-based oligosaccharides