Preheat the oven to 350 degrees F. Place baking liners in a muffin tin. NOTE: to ensure the outer liner is unsoiled using two liners per muffin can be added.
In a large bowl whisk together the flour, granulated sugar, brown sugar, baking powder and cinnamon.
Add the vegetable oil, eggs, milk, vanilla extract and orange zest; beat, on medium speed, for batter is shiny and smooth in texture (a few minutes).
Add the walnuts and cranberries and fold in to incorporate.
Divide the batter evenly between the muffin liners.
Preparing the Streusel
Prepare the streusel. In a small bowl combine the sugar, flour and cinnamon. Work in the butter until the mixture resembles coarse sand using a dough blender or dining knives. Sprinkle over the muffins.
Bake muffins for 18 to 22 minutes or until a toothpick inserted in the center comes out clean.
Cool the muffins in the pan for 5 minutes then transfer to a wire cooling rack to fully cool.
Making the Orange Glaze and glazing the muffins (optional)
If glazing the muffins prepare the glaze while the muffins cool. In a small bowl whisk together the glaze ingredients (confectioner's sugar, orange juice, vanilla extract and orange zest if using.
When the muffins have fully cooled, place a foil-lined rimmed baking sheet underneath the cooling rack. This allows excess glaze to pool in the pan underneath and not directly under the muffins which can make the liners soggy.
Dip a dining spoon into the glaze and shake it back and forth over a muffin for a light drizzle of glaze. Repeat with the remainder of glaze to glaze all the muffins. Let it until glaze sets.
Nutritional info includes the muffins and streusel topping, not the optional glaze.Storing the MuffinsLine an airtight container with a paper towel. Place the completely cooled muffins in a single layer with a second paper towel on top. Seal and store at room temperature for up to 4 days.To freeze: cool completely and add to a freezer safe airtight container or freezer bag for up to 2 months. Muffins can be individually wrapped for easier access while in the freezer.Thaw and rewarm briefly in the microwave.