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 polyoxyalkylene copolyethers obtained by copolymerization of 1,6-hexanediol and 1,12-dodecanediol which can crystallize in the entire composition range and display an isomorphic behavior. The copolymers were synthesized via a bulk self-condensation method at high temperature, using a thermally stable noneutectic mixture organocatalyst (NEMO) prepared from methanesulfonic acid (MSA) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). The final molar ratios of the copolyethers were calculated by H-1 NMR spectroscopy, and the random distribution of the two monomeric units was confirmed by C-13 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 cocrystallize regardless of the composition, while displaying melting point values that vary linearly in between those of the parent homopolymers (54.9 and 84.7 degrees 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 as isomorphic random copolymers. Finally, a random terpolymer was synthesized 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.