OJ 287 is one of the most dynamic BL Lacertae objects that has exhibited behavior representative of the entire blazar class and is also one of the best sources with simultaneous multi-wavelength coordinated data. Motivated by the strong X-ray variability exhibited by the source, we systematically investigated the simultaneous optical to X-ray emission with a focus on the spectral state of the lowest recorded X-ray flux state to understand the X-ray spectral changes. The optical-UV synchrotron emission directly traces the high-energy end of the underlying particle spectrum and its power-law continuation to X-rays can drastically affect the X-ray spectrum without much change in optical flux. Thus, the combined optical to X-ray provides a potential tool to explore particle spectrum and insights into the highest particle energies. We report the finding of a power-law optical-UV spectrum with a photon spectral index of \(2.71\pm 0.03\) continuing to X-ray energies during the lowest recorded X-ray state—also a simultaneous lowest of optical and X-rays. Accounting for this contribution at X-ray results in a photon spectral index of 1.15–1.3. We discuss the possible implications of this on X-ray spectral variations and the underlying particle spectrum.