A series of tellurite and antimonite-based glasses were synthesized to compare different heavy metal oxide glass formers in terms of vitrification behavior and thermal, physical, optical and structural properties according to the changing MoO3 concentration. Substitution of glass formers for MoO3 resulted continuous structural transformation of TeO4 trigonal bipyramid and SbO3 units. The results revealed thatMoO(3) has a dual function, i.e. former or modifier, in glass structure and in all studied glass compositions the ratio of network forming positions of MoO3 showed an increase with increasing MoO3 concentration. The direct allowed optical band gap energy values decreased with increasing temperature lying in the range 2.38 - 2.13 eV and found to be comparable with amorphous semiconductors for both glass forming systems. Antimonite glasses required higher melting temperatures and exhibited lower thermal stability and higher crystallization tendency. Therefore, tellurite glasses exhibited more suitable vitrification and thermal properties for opto-electronic applications.