Analysis of a large number of samples by electrochemical methods for rapid optimization of amperometric biosensors or screening applications is still a challenge. To overcome this limitation, a system with 96 screen‐printed electrodes was developed to assay H2O2 produced by free and immobilized galactose oxidase as a model for oxidases. Detection was based on two electrochemical methods: intermittent pulse amperometry (IPA) and electrochemiluminescence (ECL). This 96‐well electrochemical device allowed rapid optimization of the parameters in half a day, regardless of the method used (i.e., IPA or ECL). We demonstrate that ECL is more sensitive for the detection of H2O2 (limit of detection of 1 μm for ECL vs. 10 μm for IPA) with lower interelectrode variability (1 vs. 19 %). Rapid determination of sensitivities, linear ranges, and limits of detection of galactose oxidase substrates (e.g., dihydroxyacetone and l‐erythrulose) by using free or immobilized enzyme was conducted in only 50 min by the mean of 5 different sets of 96 screen‐printed electrodes.