Resistance to fenoxaprop-P and other aryloxyphenoxypropionate and cyclohexanedione herbicides in the wild oat population, UM1, is controlled by a single, partially dominant, nuclear gene. In arriving at this conclusion, parents, F1 hybrids, and F2 plants derived from reciprocal crosses between UM1 and a susceptible wild oat line, UM5, were treated with fenoxaprop-P over a wide range of dosages. Based on these experiments, a dosage of 400 g ai ha−1 fenoxaprop-P was selected to discriminate between three response types. At this dosage, susceptible plants were killed and resistant plants were unaffected, whereas plants characterized as intermediate in response were injured but recovered. Treated F2 plants segregated in a 1:2:1 (R, I, S) ratio, indicative of single nuclear gene inheritance. This was confirmed by selfing F2 plants and screening several F3 families. Families derived from intermediate F2 plants segregated for the three characteristic response types, whereas those derived from resistant F2 plants were uniformly resistant. Chisquare analysis indicated the F2 segregation ratios fit those expected for a single partially dominant nuclear gene system. In addition, F2 populations from both crosses were screened with a mixture of fenoxaprop-Pand sethoxydim. The dosages of both herbicides (150 g ai ha−1 fenoxaprop-P and 100 g ha−1 sethoxydim) were sufficient to control only susceptible plants. Treated F2 populations segregated in a 3:1 (R:S) pattern, thereby confirming that resistance to the two chemically unrelated herbicides results from the same gene alteration.