We report here an extensive direct dynamics study on the collisions of hyperthermal (14.9 kcal mol-1) atomic oxygen with a variety of graphene surfaces to explore possible reaction channels. Several models, ranging from pristine graphene to graphene with defects and with different extents of oxidation and nitridation, are investigated. The impinging oxygen atom is found to form various surface oxygenated species, such as epoxides, ethers, and lactones, as well as gaseous species, such as CO, CO2, O2, N2, CN, and NO. Some of the gaseous species have been detected in recent molecular beam studies, and our simulations help to reveal their formation mechanisms. The comparison with previous dynamical studies for a much higher O-atom incident energy (120 kcal mol-1) finds similar reactive channels and reaction mechanisms, with quantitatively different product branching ratios.