The rotational spectra of four conformers (At, Ag, Et, Eg) of the tertiary alcohol 1-methylcyclohexanol were assigned by pulsed jet Fourier transform microwave spectroscopy. The transitions of two gauche conformers were split in two separated component lines, but it was not possible-from the available measured transitions-to accurately determine their vibrational ΔE0+0- ground-state splittings, respectively. In addition, the rotational spectra of the four OD deuterated isotopologues were measured and assigned. For the gauche species of this isotopologue we were able to determine the tunneling splittings, ΔE0+0-(Ag, OD) = 15.581(5) GHz and ΔE0+0-(Eg, OD) = 18.17(3) GHz, respectively. From these splittings the inversion barriers for Ag and Eg were determined, by using a flexible model, to be B2(Ag) = 356(10) and B2(Eg) = 320(10) cm(-1), respectively.