For the first time, a laser ionization time of flight mass spectrometry (LI-TOFS) characterization has been performed on silicon oxycarbide glasses obtained by pyrolysis of solgel precursors. This technique allows to desorb intermediate range mesounits from the network, and to determine their mass and atomic identity precisely. It is therefore complementary to all the other analysis typically performed on SiOC glasses as it leads to collect information on a length scale which is usually difficult to probe: the medium range. The results indicate the presence, in the SiOC glasses, of mixed silicon oxycarbide units together with pure silicate mesounits (SiO2 and SiO3).