•A new rapid method to quantify phytosterols in fortified food was developed.•Analysis is based on gas chromatography with flame ionization detection.•The method is more economical, time and labour efficient than current methods.•Critical aspects of method validation and uncertainty are reported.•This method can ensure accurate plant sterol fortification for the food industry. A novel method for the measurement of total phytosterols in fortified food was developed and tested using gas chromatography with flame ionization detection. Unlike existing methods, this technique is capable of simultaneously extracting sterols during saponification thus significantly reducing extraction time and cost. The rapid method is suitable for sterol determination in a range of complex fortified foods including milk, cheese, fat spreads, oils and meat. The main enhancements of this new method include accuracy and precision, robustness, cost effectiveness and labour/time efficiencies. To achieve these advantages, quantification and the critical aspects of saponification were investigated and optimised. The final method demonstrated spiked recoveries in multiple matrices at 85–110% with a relative standard deviation of 1.9% and measurement uncertainty value of 10%.