The influence of eucalyptol, a bicyclic ether, on the hydrogen bond aggregation of methanol (MeOH) and 2-methyl-2-propanol (BuOH) is investigated by ragout-jet FTIR techniques. O–H stretching bands of supersonic jet cooled binary complexes are identified and compared to spectra of liquid mixtures and quantum chemical predictions. Experimental O–H stretching wavenumber shifts of mixed alcohol–eucalyptol dimers exceed those of the corresponding alcohol dimers by 76 cm⁻¹ (MeOH) and 27 cm⁻¹ (BuOH). Harmonic predictions of the wavenumber shifts at B3LYP level are found to be inconsistent among the various dimers. Experimental evidence for the cyclic nature of alcohol tetramers is presented. A microscopic explanation for the positive deviations from Raoult's law in alcohol–ether mixtures is given. Ethers are shown to be useful as hydrogen-bonded ring strain detectors and as hydrogen bonded chain termini.