Preheat your oven to 400 F (205 C) and prepare a muffin tin with cooking spray or muffin liners.
To a large bowl add the flour, oats, sugar, baking powder, baking soda and salt. Mix well to combine, then stir in the cranberries.
In a separate smaller bowl, add the egg, orange juice, melted butter and grated orange zest (or lemon zest). Mix well to combine.
Pour the wet ingredients into the dry ingredients and mix until just combined, being careful not to over mix!
Spoon the batter into the muffin tin. I got 8 big muffins (I like to fill each all the way to the top) but if you fill the tin 3/4 of the way full, you'll get 10 muffins.
Bake for 20 minutes, until the tops are firm and lightly brown. Let cool, then store in a container at room temp or in the fridge!