A reliable data set covering a parametric space of process conditions is essential for realizing catalyst informatics. A high-throughput screening (HTS) instrument was used to obtain a parametric data set to develop a detailed reaction microkinetic model for the oxidative coupling of methane (OCM) over a La2O3/CeO2 catalyst. The model was combined with well-validated gas-phase kinetics to describe the interactions between homogeneous and heterogeneous reaction chemistry. Methane and oxygen conversions and selectivities of ethylene, ethane, carbon monoxide, and carbon dioxide were measured experimentally in the temperature range of 500 to 800°C, CH4/O2 ratio between 3 and 13, and pressure between 1 bar and 10 bar. The proposed reaction network consists of 52 irreversible elementary steps describing catalytic reactions between 11 surface species and 123 reversible steps describing the contribution of gas phase between 25 species. A packed-bed reactor model was developed based on the dimensions of the experimental setup and catalyst characterization results to account for homogeneous-heterogeneous interactions. The proposed mechanism was tested and validated over a wide range of operating conditions and showed a reasonable fit with an average difference of less than 5% compared to experimentally measured methane conversion and selectivities of ethylene and ethane. Rate of production (ROP) and species sensitivity analyses were performed to identify the main reaction pathways and highlight the important reactions in the OCM.