During IVM, low oxygen with low glucose and a lower volume of medium per COC, significantly reduces oocyte developmental competence, which is rescued by increasing volume of medium available per COC. Blastocyst rate (% from starting number of COCs) of bovine embryos developed from oocytes matured in two different oxygen concentrations, and two different volumes of media per COC (Experiment 2, 2×2 factorial design). Data presented as mean ± SEM (n = 5 independent replicates with 40±5 COCs/treatment group/replicate). Means with different superscripts indicate significant differences between treatment groups (P < 0.05)