Preheat Oven and Prep Pan:
Heat the oven to 375°F (190°C). Place paper liners in a 12-cup muffin pan or coat the cups with a light layer of grease.Whisk Wet Ingredients:
In a large mixing bowl, combine 1 cup Greek yogurt, ¼ cup milk, ⅓ cup honey (or maple syrup), 1 egg, 2 Tbsp vegetable oil, and 1 tsp vanilla extract. Whisk until the mixture is uniform.Mix Dry Ingredients:
In a separate bowl, mix 1 cup rolled oats, ¾ cup all-purpose flour, 1 tsp baking powder, ½ tsp baking soda, 1 tsp cinnamon (optional), and ¼ tsp salt. Stir to distribute evenly.Combine Wet and Dry:
Pour the dry mixture into the wet mixture and stir until they are just incorporated. Avoid overmixing.Fold in Blueberries:
Carefully fold 1 cup fresh blueberries (or frozen) into the batter. Portion the batter into the prepared muffin cups, filling each to about three-quarters full.Bake Muffins:
Bake for 18–20 minutes, until the tops are golden and a toothpick inserted into the center comes out clean.Cool in Pan and Rack:
Allow the muffins to sit in the pan for 10 minutes, then move them to a wire rack to finish cooling.