Preheat and prep the muffin pan. Preheat the oven to 350 degrees F and grease a 12 cup muffin tin or use a silicone muffin pan.
Mix the wet ingredients. In a large bowl, mix the Greek yogurt, pumpkin puree, eggs, milk, maple syrup, and vanilla extract with a whisk until well combined.
In a separate bowl, stir together the oats, baking powder, salt, and pumpkin pie spice. Combine these dry ingredients with the wet. Now fold in the chocolate chips.
Divide the batter evenly among the 12 muffin cups and fill all the way to the top.
Bake for 22 - 24 minutes or until set and a toothpick inserted in the center comes out clean. Let cool in the pan for 5 - 10 minutes before removing.
Serve warm, or cool completely and store in the fridge for up to 5 days, or freeze for up to 3 months.