The objective of this study was to assess the effects of microbial inoculation and particle size on fermentation profile, aerobic stability, and ruminal in situ starch disappearance of high-moisture corn. High-moisture corn (HMC) was harvested, either coarsely or finely ground (3797.8 vs. 984.1 ± 42.4 μm, on average, respectively), and inoculated with distilled water (CON), Lactobacillus plantarum CH6072 at 1 × 10⁵ cfu and Enterococcus faecium CH212 at 5 × 10⁴ cfu/g of fresh forage (LPEF), or L. buchneri LB1819 and Lactococcus lactis O224 at 1.5 × 10⁵ cfu/g (LBLL). Silos were ensiled in quadruplicate vacuum pouches for 0, 14, or 28 d. Data were analyzed as a completely randomized design with a 2 × 3 × 3 factorial arrangement of treatments using PROC GLIMMIX. The model included particle size, microbial inoculation, storage length, and their interactions as fixed effects. An interaction between microbial inoculation and storage length was observed for lactic acid (P = 0.001). Concentrations of lactic acid were similar among all inoculant treatments at 0 d, greatest in LPEF and lowest in LBLL at 14 d, and lower in LBLL compared with CON and LPEF (0.93 vs. 1.73 ± 0.04% of DM) at 28 d. A 3-way interaction between particle size, microbial inoculation, and storage length was observed (P < 0.05) for acetic acid. At 14 and 28 d, acetic acid concentrations were greatest in Fine LBLL, followed by Coarse LBLL, Fine CON, and Fine LPEF, and lowest for Coarse CON and Coarse LPEF. Ruminal in situ starch disappearance was greater (P < 0.05; 57.5 vs. 51.5% of starch, on average, respectively) with LBLL compared with CON and LPEF. Likewise, greater aerobic stability was observed (P < 0.05; 224.8 vs. 44.5 h, on average, respectively) with LBLL compared with CON and LPEF. These results suggest that certain strains of L. buchneri produce acetic acid, improve aerobic stability, and increase starch disappearance of HMC within 28 d of fermentation.