Preheat oven to 350 degrees F (175 degrees C). Lightly coat a baking sheet with cooking spray.
In a bowl, thoroughly mix the milk and prepared brown mustard. In a separate bowl, mix the oats, sage, and rosemary. Dredge each turkey breast first in the milk mixture, then in the oat mixture to evenly coat.
Bake turkey 30 minutes in the preheated oven, until the oats are crisp and the internal temperature of the turkey has reached a minimum of 180 degrees F (80 degrees C).
In a bowl, mix the yogurt and whole grain mustard. Season with salt and pepper. Drizzle over the cooked turkey to serve, or use as a dipping sauce.
