Well-dispersed bimetallic nanoparticles (BMNPs = PtPd/AuPd/AuPt) confined in mesoporous metal oxides (MMOs = TiO₂/Al₂O₃/SiO₂/ZrO₂) are synthesized by a general and mild one-step sol–gel strategy. This approach allows facile control over the compositional parameter of the supported BMNPs and the MMOs. Moreover, we can also control the formation of the alloy by simply adjusting the loading content. The catalytic results of PtPd–MMO composites in the hydrogenation of nitrobenzene have shown that the performance is highly composition-dependent and support-dependent with Pt₁Pd₃–m-SiO₂ showing the optimum activity.