Oxazolidinones have been synthesized by reacting glycerol carbonate or glycerol with urea in the presence of γ-Zr phosphate as a catalyst. The conversion yield of the polyol or its carbonate depends on the temperature. Below 408 K the selectivity is 100 % with a conversion of up to 25 %, whereas increasing the temperature means that conversion yield grows, but the selectivity decreases, which makes the separation process more difficult. Starting from glycerol carbonate, two isomers, 6 and 6′, are formed with a quasi 1:1 molar ratio because urea can attack the carbonate moiety on both sides of the carboxylic CO moiety. From glycerol the formation of the 6′ isomer is preferred: the ratio of 6′/6 is close to 7. The oxazolidinones formed act as templates because they interact through hydrogen bonding with glycerol. The intensity of the interaction depends on the 6 or 6′ isomer: DFT calculations showed that the energy was 22.6 kcal mol−1 for 6-oxazolidinone and 25.7 kcal mol−1 for 6′-oxazolidinone.