A detailed description of the electronic properties, chemical state, and structure of uniform single and few-layered graphene oxide (GO) thin films at different stages of reduction is reported. The residual oxygen content and structure of GO are monitored and these chemical and structural characteristics are correlated to electronic properties of the thin films at various stages of reduction. It is found that the electrical characteristics of reduced GO do not approach those of intrinsic graphene obtained by mechanical cleaving because the material remains significantly oxidized. The residual oxygen forms sp(3) bonds with carbon atoms in the basal plane such that the carbon sp(2) bonding fraction in fully reduced GO is similar to 0.80. The minority sp(3) bonds disrupt the transport of carriers delocalized in the sp(2) network, limiting the mobility, and conductivity of reduced GO thin films. Extrapolation of electric conductivity data as a function of oxygen content reveals that complete removal of oxygen should lead to properties that are comparable to graphene.