Steam reforming of simulated bio-oil (ethanol, acetone, phenol, and acetic acid) and phenol has been studied on K-Ni-Cu-Mg-Ce-O/Al2O3 composite catalysts. Complementary characterization techniques, such as nitrogen sorption, XRD, H-2-TPR, H-2-TPD, CO-TPD, CO-DRIFTS, and in situ XPS, were used to correlate surface structure and functionality to catalytic performance of potassium (K) doped catalysts. K doping of the Ni-Cu-Mg-Ce-O/ Al2O3 catalyst created a Ni degrees/Ni2+ mixed active phase, which not only enhanced steam reforming activity, but also suppressed the methanation reaction. In addition, K doping changed the surface acid-basic properties of the catalyst, which instead favor the gasifcation and water-gas shift reactions. With the combination of these effects, K doping of Ni-Cu-Mg-Ce-O/Al2O3 catalysts led to higher C1 yield and much lower methane formation, favoring hydrogen production in steam reforming of both phenol and simulated bio-oil.