For the first time, rotational constants along with centrifugal distortion constants have been determined for OThS and OCeS. The rotational spectra of these molecules and, in each case, one other isotopologue (OTh34S and O142CeS) were produced utilizing a laser ablation sourcing technique incorporated into a chirped-pulse Fourier transform microwave spectrometer operating in the 8 to 18 GHz region of the electromagnetic spectrum. The bent structures determined are in very good agreement with theoretical calculations. Comparisons between atomic coordinates, bond lengths and angles, as well as the inertial defect are discussed.