Isomorphism in random copolymers occurs when comonomer units can crystallize within a single crystalline lattice in the entire composition range. This ideal behavior is rare in random copolymers and only a few examples of isomorphism are found in copolyesters and copolycarbonates. In this work, we show a series of polyoxyalkylenes copolyethers obtained by copolymerization of 1,6hexanediol and 1,12-dodecanediol which are able to crystallize in the entire composition range and display an isomorphic behavior. The copolymers were synthesized via a bulk selfcondensation method at high temperature, using a thermally stable Non-Eutectic Mixture Organocatalyst (NEMO) prepared from methanesulfonic acid (MSA) and 1,5,7triazabicyclo[4.4.0]dec-5-ene (TBD). The final molar ratios of the copolyethers were calculated by 1 H NMR spectroscopy and the random distribution of the two monomeric units was confirmed by 13 C NMR spectroscopy. The effect of the composition of comonomer units on the crystalline structure was investigated by DSC and WAXS. The two comonomeric units along the chain can co-crystallize regardless of the composition, while displaying melting point values that vary linearly in between those of the parent homopolymers (54,9 and 84,7 °C). The crystalline reflections given by WAXS demonstrated that the two comonomers are miscible in the crystalline state and meet the general criteria to be regarded isomorphic random copolymers. Finally, a random terpolymer was synthetized from 1,6-hexanediol, 1,10-decanediol and 1,12-dodecanediol, which also shows a single melting temperature, thus demonstrating the versatility of the polymerization route employed.