Preheat Oven: Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease with cooking spray.
Mix Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, salt, and orange zest.
Combine Wet Ingredients: In a separate bowl, whisk together the orange juice, milk, vegetable oil, eggs, and vanilla extract until smooth.
Mix the Batter: Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Be careful not to overmix; the batter will be slightly lumpy.
Fill the Muffin Tin: Divide the batter evenly among the muffin cups, filling each about 3/4 full.
Bake: Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.
Make the Glaze (Optional):
Prepare the Glaze: In a small bowl, whisk together the powdered sugar and orange juice until smooth. Stir in orange zest for extra flavor if desired.
Glaze the Muffins: Drizzle the glaze over the cooled muffins or dip the tops into the glaze for a glossy finish. Let the glaze set for a few minutes before serving.