We report on our latest results in the calculation of the two–mass contributions to 3–loop operator matrix elements (OMEs). These OMEs are needed to compute the corresponding contributions to the deep-inealstic scattering structure functions and to generalize the variable flavor number scheme by including both charm and bottom quarks. We present the results for the non-singlet and Agq,Q OMEs, and compare the size of their contribution relative to the single mass case. Results for the gluonic OME Agg,Q are given in the physical case, going beyond those presented in a previous publication where scalar diagrams were computed. We also discuss our recently published two–mass contribution to the pure singlet OME, and present an alternative method of calculating the corresponding diagrams.