Pre-heat the oven to 180°C (fan)/200°C/gas mark 6. Grease a 20 x 30cm baking tin and line with non stick baking parchment.
Place 250g oats, 250ml milk, 2 small mashed bananas, 1 tsp ground cinnamon and 2 tbsp maple syrup (if using) in a mixing bowl.
Mix well with a wooden spoon until all the oats are coated in the milk and banana mixture.
Add the blueberries and gently mix in.
Scrape the mixture into your prepared baking tin and press down well so the surface is flat. Press in any blueberries that are too close to the edge.
Bake in the preheated oven for 20-25 minutes until turning golden brown on top.
Remove from the oven and allow to cool in the tin before cutting into 12 bars. If your baby is very young you may want to cut into smaller bars but make sure they're big enough to be gripped.
Store in an airtight container in the fridge for up to three days or in the freezer.