Orbital Hall magnetoresistance (OHMR) effect provides a powerful platform for investigating orbital current transport and the coupling between orbital angular momentum and magnetization, and has recently emerged as an important topic in spin–orbitronics. In conventional light-metal/ferromagnet heterostructures, however, the OHMR signal is typically weak due to the intrinsically low efficiency of orbital-to-spin current conversion and limited interfacial transparency, all of which hinder effective transfer of angular momentum to the magnetic layer. In this work, Cr(t)/Co/Pt₃ multilayers were fabricated by magnetron sputtering, and their OHMR were systematically investigated at room temperature. In this structure, orbital currents are generated via the orbital Hall effect in the light metal Cr layer. The presence of Pt, a heavy metal with strong spin–orbit coupling, plays a dual role: it enhances orbital-to-spin conversion efficiency through spin–orbit interaction, leading to a pronounced modulation of longitudinal resistance via spin-dependent scattering processes. Consequently, a sizable OHMR of 1.6×10⁻³ is achieved at room temperature, which is approximately one order of magnitude larger than previously reported values in similar systems. By quantitatively analyzing the dependence of OHMR on Cr thickness using the spin-diffusion model, the effective orbital diffusion length in Cr is extracted to be approximately 0.93 nm. This value is significantly shorter than earlier experimental reports, suggesting that orbital transport in Cr is highly localized and likely dominated by rapid orbital relaxation processes. This observation supports a picture in which orbital angular momentum decays over sub-nanometer length scales rather than propagating over long distances. Furthermore, in Cr/Pt/Co/Pt multilayers, the insertion of a Pt spacer layer between Cr and Co enables more efficient conversion of orbital currents into spin currents. At the same time, the spin Hall effect in the top Pt layer generates an additional spin Hall magnetoresistance (SHMR) contribution. The coexistence and synergistic interplay between OHMR and SMR significantly enhance the overall magnetoresistance, yielding a large value of 4.5×10⁻³, far exceeding that of conventional heavy-metal/ferromagnet bilayers. These results provide important experimental insights into the microscopic mechanisms governing orbital current generation, diffusion, and conversion, and highlight the crucial roles of spin–orbit coupling in optimizing magnetoresistance effects. This work thus offers valuable guidance for the design of high-efficiency, low-power spin–orbitronic devices based on orbital physics.