Add oats and butter to the bowl of a stand mixer or large mixing bowl. Heat milk to a simmer and pour on top, stirring to combine. Set aside for about 1.5 hours. Mixture should be at room temperature.
Add honey, warm water, instant yeast, and salt to the bowl and stir well to combine. Add the whole wheat flour and mix on medium-low speed until combined. Add the all-purpose flour, a little at a time, until the dough begins to pull away from the sides of the bowl. Only add enough flour to make a dough that is soft, and not overly sticky (don’t add too much flour!). Knead for a few minutes until smooth and elastic and scrape down the sides and bottom of the bowl as needed.
First Rise: Transfer dough to a greased bowl and cover with a dish towel or plastic wrap. Allow to rise until double in size, about 1 hour.
Punch down the dough and divide into two equal pieces. Shape into loaves and place in two lightly greased loaf pans. Make egg wash and gently brush some over the top of each loaf. Sprinkle a small handful of dry oats on top.
Second rise: Cover with a well greased piece of plastic wrap gently laid on top and let rise in a warm place until risen about 1 inch over the loaf pans, 45 minutes to 1 hour. Carefully peel off the plastic wrap.
Bake at 350 degrees for 30 – 40 minutes. Loaves are done when tapping lightly on the tops produces hollow sound (or when instant read thermometer registers 200° F). Cool for 15 minutes on wire rack, then turn out of pans and cool completely.
To make in a bread machine: You may want to halve the recipe to make one loaf, depending on the capacity of your bread machine.Vegan/Dairy-free oat bread: Substitute dairy free butter and almond milk, and omit the egg wash.For Active dry yeast: If you know your yeast is fresh it's not necessary to proof the yeast in this recipe. Simply substitute an equal amount and add it in place of instant yeast.Make ahead Instructions: Make the bread dough through step 2, before the first rise. Place in a large airtight container, and refrigerate for up to one day. Remove from fridge and allow to come to room temperature. Proceed with punching down and forming loaves.To freeze bread dough: Prepare the recipe through step 3, before the second rise. Place the shaped loaves into a freezer-safe or disposable aluminum bread pan. Cover tightly with a double layer of aluminum foil and freeze for up to 3 months. When ready to bake, allow the loaves to thaw and complete the second rise, at room temperature (about 5 hours). Bake as directed.To freeze baked bread: Allow baked bread to cool completely. Place each loaf in a freezer-safe resealable bag and freeze for up to 3 months. Thaw at room temperature on the countertop, or overnight in the refrigerator.