Aspergillus oryzae is a saprotroph that is used in solid-state fermentations (SSFs) to produce plant-based foods. Much remains unknown about how this fungus colonizes organic substrates. Here, we studied colonization of A. oryzae on whole yellow pea (Pisum sativum) using different inoculum sizes (2.4, 2.4 102, and 2.4 105 spores g-1 dry weight peas). Fluorescence microscopy of the GFP expressing strain A. oryzae RB#140.1 showed that the fungus colonized the peas both externally and internally regardless of inoculum size. However, the highest inoculum size showed higher pea biomass reduction when compared to the low inoculum size, while spore formation decreased with increasing inoculum size. Proteomic analysis of aqueous extracts of the colonized peas revealed that the secretomes resulting from the different inocula were similar. Amylases, proteases and enzymes active on cellulose , pectin, glycoconjugates, oligosaccharides, and lipids were found in the three top 25 secreted proteins. Indeed, amylase, cellulase, and pectinase activity were similar in the three aqueous extracts and xylanase activity was low. By contrast, the protease activity was higher in the intermediate inoculum size when compared to the highest inoculum size. Proteomics also showed β-1-3-glucanase and chitinase enzymes within the three top 25s of secreted proteins, indicative of hyphal lysis. Indeed, a large part of proteins in the aqueous extract did not have signal sequences for secretion. Together, high inoculum size is preferred to convert pea biomass and to obtain low sporulation without having a strong effect on the secretome when compared to the intermediate and low inoculum sizes.