Maturational events in ovarian follicles that lead to the attainment of developmentally-competent oocytes are not fully understood. To investigate these events in low OR species is problematic as normally, only 1-2 follicles ovulate each reproductive cycle. To overcome this, we investigated the morphological and molecular characteristics of granulosa cells (GC), cumulus cells (CC) and oocytes in both growing and ‘presumptive pre-ovulatory’ follicles in ewes with normal (++) and high (I+B+) OR. We hypothesised that follicles with expanded CC-oocyte complexes were ‘presumptive pre‑ovulatory’ follicles and that functional similarities in these follicles between the genotypes signify some of the key events involved during the final maturational stages. Ewes (++: N=10, OR=1-3; I+B+: N=9, OR=4-8) had CIDRs inserted for 10 days. Prostaglandin F2α was administered 24h before, and ovaries were collected 52h after, CIDR removal. From each individual follicle ≥1mm in diameter, CC and denuded oocytes, as well as GC were collected for analyses of gene expression and cAMP responses to gonadotrophins, respectively. The diameters of pre-ovulatory follicles were smaller (P<0.0001) in I+B+ (3.5±0.1mm) compared to ++ (5.7±0.6mm) ewes. In pre-ovulatory follicles, cAMP responses of GC to gonadotrophins were not different between genotypes when standardised for GC number, but total cAMP was increased (P<0.0001) in ++ ewes, due to greater GC numbers/follicle. Expression of key genes involved in late maturational events (e.g. HAS2, VCAN, PGR) was increased in expanded, compared to non-expanded, CC and were similar between genotypes. Expression of a regulatory gene involved in protein processing (HSP90B1) was decreased (P<0.0001) in non-expanded, compared to expanded, CC in I+B+ ewes, but was similar between genotypes in expanded CC, and between expanded and non-expanded CC in ++ ewes. In summary, the genes involved in key maturational events were similar in pre-ovulatory follicles regardless of genotypic differences in OR and pre-ovulatory follicle size.