Lower developmental capacity of the in vitro-matured oocyte is due to asynchronous between nuclear and cytoplasmic maturation. Oocytes that are artificially removed from the antral follicle resume meiosis spontaneously while the cytoplasm still has not acquired the capacity necessary to support fertilization and early embryonic development. Temporary delaying of spontaneous nuclear maturation might improve the quality of the cytoplasmic development and finally improve the developmental competence of IVM oocytes. Studies show that the cAMP plays an important role in the regulation of mammalian oocyte maturation. High concentrations of cAMP inside the oocyte lead to meiotic arrest, whereas meiosis resumption of the oocyte depended to low concentrations of the cAMP within the oocyte. In an effort to improve the developmental competence of IVM oocytes by controlling nuclear and cytoplasmic maturation have mainly concentrated on a ‘biphasic IVM’ strategy. Hence the present study was designed to evaluate the effect of adenylate cyclase activator (Forskolin) on meiotic resumption and developmental capacity of ovine immature oocytes. Ovine COCs were first used for routine IVM and stepwise pattern of nuclear maturation was evaluated at 2 h intervals. Then, immature COCs were cultured in pre-IVM medium in the presence of different concentrations of Forskolin (10, 50, 100, 200, 300, and 400) and at three important pre-IVM intervals, determined in the former experiment (6, 8 and 22 hour after pre-IVM), and the nuclear status and microtubule organizations of the oocytes were assessed. Then the effect of selected Forskolin concentration on dynamic of nuclear status during critical stage of GV to GVBD transition was assessed at 1h intervals (0 to 6 hour) during pre-IVM. Finally, to assess the effect of Forskolin on oocyte competence, treated (selected Forskolin concentration) and non-treated (control) oocytes were subjected parthenogenetic activation (PA). In this study, owing to successful application of Forskolin in GV-maintenance in cattle oocytes, we used Bovine oocytes as external control. Bovine COCs were first used for routine IVM and stepwise pattern of nuclear maturation was evaluated, then we exposed bovine COCs in pre-IVM medium with 50 and 100 µM Forskolin and oocyte meiotic status was assessed after 8 and 22 h in pre-IVM. The results revealed that By 8 h, metaphase I had occurred in most oocytes. At 16 h, most of the oocytes were at anaphase I and telophase I and at 22 h, most oocytes had reached metaphase II. No significant difference was observed in the percentages of oocytes that were maintained at the GV stage after 6, 8or 22 hours in pre maturation culture. It was observed that 300 and 400 µM concentrations of Forskolin were toxic. Therefore, based on these results concentration 50µM Forskolin was chosen. Our results show Forskolin only induces 2h delay in meiotic resumption in ovine. Cumulus expansion was not affected by Forskolin. Investigation of embryonic development via PA showed that in the control group, cleavage rate was reduced while Blastocyst rate of oocytes treated with 50 µM Forskolin was significantly lower than control group. In this study also, bovine oocytes arrested in the GV stage by 8 h of culture with 50 and 100 µM forskolin, hence forskolin only transiently blocked GV; by 22 h of culture approximately no oocytes were arrested at the immature GV stage. Keywords : In vitro maturation, Two-step culture, Forskolin, Embryonic development