Novozym 435 (Candida antarctica lipase)-catalyzed glycerolysis of commercial oils and fats to produce monoglycerides (MGs) was investigated using a tetraammonium-based ionic liquid (IL) as a reaction medium. A 90% yield of MGs and nearly 100% conversion of triglycerides in this ionic liquid were achieved, markedly higher than in normal solvents. The amphiphilic structure of cocosalkyl pentaethoxi methyl ammonium methosulfate (CPMA·MS) was suggested to be capable of creating a compatible system for glycerol, oils and fats, as well as inducing the shift of reaction equilibrium to the formation of MG. Interestingly, over a wide range of solvent dosage, the higher yields of MG were observed, indicating the good bulky substrate-tolerating capacity of the IL. The universal validity of the protocol was verified by being successfully applied to different commercial oils and fats. Excellent operational stability of the lipase and the reusability of IL were also observed in consecutive batchwise reactions. The results indicate that the protocol developed in this work provides a new environmentally benign “solution” to the enzymatic modification of fats and oils with industrial potentials.