Graphene oxide (GO) is well known as a key material to the commercialization of graphene-based applications due to its excellent processability and abundant starting materials. However, producing high quality GO with excellent structural intactness still remains a challenge despite the significant research effort over the past decade. Herein, we demonstrate an effective approach to achieving well-oxidized GO within only 5 h of oxidation time at 5 °C or 25 °C from expanded graphite as a starting material. Our finding reveals that the well-oxidized GO synthesized at 25 °C can regain more graphitic sp2 networks and thus becomes as conductive as the GO prepared at 5 °C by means of thermal annealing or green chemical reduction. We also found that green chemical reduction using vitamin C (VC) is more efficient in restoring the electrical conductivity and reducing the defects in the GO produced at room temperature. The protocol reported in this paper offers a promising, sustainable way to fabricate high quality GO with minimal energy input, while being cost-effective.