Preheat oven to 325°F Line two large baking sheets with parchment paper or silicone baking mats.
In a large bowl, gently mix the peanut butter, milk, and egg together with a wooden spoon or rubber spatula. Add the flour and baking powder. You may need to turn the dough out onto a floured work surface and use your hands to work in the flour. Mix in the oats and bacon. The dough is extremely thick and heavy.
Using a floured rolling pin, cut into shapes using cookie cutters or a knife. Arrange on the baking sheets. Bake for 18-20 minutes, or until very lightly browned on the bottom. Remove from the oven and flip the treats to bake the other side for 10-12 more minutes.
Allow to cool completely before serving to your pup. Cover and store leftovers at room temperature for up to 1 week or in the refrigerator for up to 2 weeks. The treats freeze well for up to 2 months as well.