Preheat the oven to 350°F (180°C). Line a muffin tin with liners or use a silicone muffin tray.
Place all the ingredients together in a large bowl and mix until well combined.
Transfer about ¼ cup of the batter into each muffin case. Place into the hot oven and bake for 35-40 minutes, until cooked through and a cocktail stick inserted into the center of the cake comes out clean.
Set the tray onto a wire rack and allow the oatmeal cups to cool, before removing from the liners.