Stir together the oats and milk in a medium bowl. Stir. Set aside for 15 minutes to let the oats soak up some of the milk while you prepare the rest of the pancake ingredients.
Place the butter in a small bowl and melt in the microwave (or melt on the stove). Set aside.
Meanwhile, in a medium bowl, whisk together the flour, baking powder, baking soda, salt and cinnamon.
In a large bowl, combine the eggs, plain Greek yogurt, honey (or pure maple syrup) and vanilla. Whisk until smooth. Then whisk in the melted butter. Use a rubber spatula to stir in the oat and milk mixture.
Pour the dry ingredients into the wet ingredients. Use the rubber spatula to mix until just combined, being careful to not over-mix the batter.
Heat an electric griddle or non-stick skillet over medium heat (325° F). Grease the griddle or skillet with cooking spray, if it requires greasing.
Use a ¼ cup measuring cup to scoop scant ¼ cups of the pancake batter onto the griddle (the ¼ cup measuring cup should be about ¾ full). Let pancakes cook on the first side until bubbles form and the pancake bottoms are golden, 3-5 minutes. Flip the pancakes and cook them on the second side until golden, about 2 minutes. Serve pancakes with maple syrup, if desired.