High-throughput synthesis and screening of mixed metal oxide libraries for ethane oxidative dehydrogenation to ethylene have been developed. A 144-member catalyst library was prepared on a 3 in. quartz wafer. An apparatus for screening catalytic activity and selectivity of a 144-member catalyst library consists of a reaction chamber, where each member can be heated individually by a CO2 laser and reactant gases can be delivered locally to each member. The reaction products, ethylene and CO2, are detected by photothermal deflection spectroscopy and by mass spectrometry. A 144-member catalyst library can be screened in slightly more than 2 h. V-Al-Nb oxide and Cr-Al-Nb oxide libraries are illustrated as examples. V-Al-Nb oxide catalysts are high temperature catalysts and Nb did not affect the catalytic activity of the V-Al oxides in contrast to the effect of Nb found in Mo-V-Nb oxides. However, for the Cr-Al-Nb oxide library, the most active catalyst contains about 4% Nb. These results suggest that a fine composition mapping is necessary for discovery of new heterogeneous catalysts in those ternary systems.