Preheat the oven to 350°F degrees. Thoroughly grease the muffin cups or pan with butter. Combine the dry ingredients in a mixing bowl and drizzle with the warm butter, stir to combine.
Add the eggs, stir and then add the milk. Stir to combine everything and then stir in about ⅔ of the peaches, reserving a few peaches for the top of the oatmeal.
Scoop the mixture into the muffin cups or pour it into the pan. Bake the muffin cups for about 20-25 minutes, until an inserted knife comes out with only moist oatmeal crumbs. (An 8x8 pan of oatmeal will take about 35 minutes.) Serve warm.
Notes
FREEZER MEAL: Let the oatmeal cool completely and then store the oatmeal in airtight freezer bags or containers. Reheat in the microwave with a tablespoon of water.