Over the past decade, the trans-fat content of foods has become increasingly important to consumers. FTIR-ATR spectroscopy provides an efficient analytical tool to measure the percentage of trans-fat in several commercially available lipids. Instrument calibration is easily established using pure cis and trans isomeric standards. The degree of alkene isomerization induced by bromination–debromination chemical reactions is also determined using this analytical method. We describe a simple analytical method for determining trans-fat content in cooking oils, using FTIR-ATR. This activity generates high interest among students and is appropriate for instrumental laboratories in analytical, biochemistry, nutritional, and organic chemistry courses.