The IR absorption spectra of liquid OCS (T = 135(1) K) and of the following solutions-OCS + Ar (T = 90 K), OCS + N ₂ (T = 90 K), OCS + Kr (T = 130 K), and OCS + Xe (T = 163 K)-are measured in the range 800-7000 cm ^-1 . From 16 to 40 bands corresponding to transitions to vibrational states up to the third order inclusive are interpreted for basic isotope modification and for the isotopically substituted molecules ¹⁸ O ¹² C ³² S, ¹⁶ O ¹³ C ³² S, and ¹⁶ O ¹² C ³⁴ S. In the spectra of the liquids, the spectral moments M(1) and M(2) of all the observed bands are determined. The harmonic frequencies ω _i and the anharmonicity constants x _ik are calculated for all the systems, including the liquid. The anharmonicity is found to be constant within the experimental error. A large shift Δω ₃ is primarily determined by the dipole-induced dipole interaction.