<p>This study uses a computational method called Density Functional Theory (DFT) to examine the structure, electronic, optical, elastic, and magnetic properties of Sr₂GdMO_<b>6</b> (M = Bi or Sb). The calculations revealed that both materials have a cubic crystal structure with slightly different lattice constants. Volume optimization of Sr₂GdBiO₆ and Sr₂GdSbO₆ in PM, FM, and AFM states reveals that Sr₂GdBiO₆ stabilizes in a non-magnetic PM phase, while Sr₂GdSbO₆ favors a magnetic ground state. The magnetic behavior is influenced by the B-site cation, with Bi suppressing and Sb promoting magnetic ordering. Their electronic structures reveal that Sr₂GdBiO₆, have band gap 2.06 eV for spin-up and 2.18 eV for spin-down. Similarly, Sr₂GdSbO₆, have band gap 3.26 eV for spin-up and 3.40 eV for spin-down. Optical investigations have shown strong absorption in the ultraviolet region, with peaks at 3.75 eV for Sr₂GdBiO₆ and 4.15 eV for Sr₂GdSbO₆. The materials Sr₂GdBiO₆ and Sr₂GdSbO₆ have stable mechanical properties, with bulk moduli of 112.18 GPA and 143.235 GPA, respectively. They possess a significant magnetic moment of 7 Bohr magnetons per gadolinium atom, primarily due to the contribution of its 4f electrons, indicating their strong magnetic nature. To accurately account for the interactions between electrons in these materials, a specific parameter called the Hubbard parameter (U) was adjusted to 6 electron volts (eV) for the Gd-4f orbitals. These findings demonstrate their potential applications in spintronics, ultraviolet optoelectronics, and mechanical devices.</p>