Zest the orange into small strips using a zester. Half and juice the orange.
Place the rolled oats, cinnamon, milk, vanilla extract, orange juice and half of the orange zest into a medium saucepan. Heat over medium heat, stirring regularly, until the mixture comes to the boil. Once boiling, reduce heat and simmer, stirring often, for around 10 minutes until the oats have thickened.
While the oat mixture is cooking, place the frozen berries and 1 Tablespoon of water in a small saucepan. Heat on medium heat for 3-4 minutes until berries soften.
Spoon the oat mixture into serving bowls and top with berries and extra orange zest for garnish.
Notes
This recipe makes 4 serves. If you are want enough for 2, you can simply halve the recipe.