Catalyzes the oxidation of glycolate to glyoxylate, with a reduction of O2 to H2O2. May use other 2-hydroxyacids as substrates. glycolate + O2 = glyoxylate + H2O2 a (2S)-2-hydroxycarboxylate + O2 = a 2-oxocarboxylate + H2O2 Binds 1 FMN per subunit. Homotetramer. Belongs to the FMN-dependent alpha-hydroxy acid dehydrogenase family.