Radical chemistry is a fundamental subject of undergraduate organic chemistry. While well described in organic textbooks, laboratory manuals rarely address this topic, focusing instead on syntheses using polar reactions. Herein, we describe a colorimetric assay using the persistent radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) to measure the antioxidant activity of common antioxidants in one (3 hour) lab period. While the laboratory procedures are designed for a second-year organic laboratory environment, minor modifications to either the experiment or the supplemental material would make this suitable for more or less advanced courses. This exercise is particularly appropriate for a course geared for nutrition or food science majors. (Contains 1 figure, 1 scheme, 1 table and 2 notes.)