Preheat your oven to 400°F (200°C).
Line a muffin tin with paper liners or grease it lightly.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.
In another bowl, mix the egg, milk, vegetable oil, and orange zest.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Gently fold in the cranberries.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake for 18-22 minutes or until a toothpick inserted comes out clean.
Let the muffins cool in the pan for 5 minutes before transferring to a wire rack.