This research shows that the existing literature on milk marketing orders misses an important effect. Previous work ignores the interaction of marketing orders with milk grading regulation. We model this interaction and show that producer benefits from marketing orders have been smaller than previous work suggests, and, under some conditions, may even be negative. Additional costs of producing fluid grade milk, omitted from previous welfare analyses, reduce producer benefits from marketing orders. Estimates of the additional cost indicate that this previously unmeasured effect is a significant component of the total welfare effect of marketing orders. An econometric model is developed to explain the variation in the fluid grade share of milk across states and time as a function of marketing order policy. Regression results support the hypothesis that marketing orders have encouraged the shift towards production of fluid-grade milk.