Experimental milling studies of environmental and genetic variation in wheat have often used small mills with one to several flour streams. Using Allis Chalmers commercial mill stands to produce commercial straight grade flour, we have sought to quantify the reproducibility of milling characteristics of 35 soft wheat cultivars grown in Virginia for 2 to 5 years. Years and genotypes were considered as random effects in the analysis of variance. The magnitude of the F-test of genotypes to genotype x year interaction was used as measure of relative reproducibility of milling and flour characteristics. Straight grade flour yield of genotypes had an F-value of 8.0 (p<0.001), with a standard error of 4 g/kg for a single milling observation of a single cultivar. Break flour yield of genotypes had a similar level of significance to straight grade flour yield (F= 8.2, p<0.001), with a 13 g/kg standard error of a single observation. Flour protein had the lowest genotypic significance with an F-test of 2.9 (p<0.05), with a 6 g/kg standard error of a single observation. Milling using large scale mills produces flour measurements with genotypic variances that are much larger than genotype x year variances. With appropriate use of checks, one to several experimental milling evaluations can accurately distinguish differences of significantly less than 10 g/kg for flour yield.