Preheat oven to 350°F and line muffin tin with paper liners or grease with nonstick spray.
In a large mixing bowl, whisk together flour, brown sugar, baking powder, baking soda, salt, and cinnamon.
In a separate bowl, mix together avocado oil, sourdough discard, vanilla extract, Greek yogurt, eggs, and orange juice.
Pour wet ingredients into dry ingredients and stir until just combined.
Gently fold in cranberries and chopped oranges.
Scoop batter into muffin tin, filling each cup to the top.
Bake for 18–20 minutes, or until muffins are golden brown and a toothpick comes out clean.
Cool muffins in the pan for 5 minutes, then transfer to a wire rack to cool completely.
In a small bowl, whisk together powdered sugar, orange juice, and vanilla for the glaze.
Drizzle glaze over cooled muffins and let it set before serving.
