Oats are a great first food for babies for those who are going down the purée and cereal route like me.
It’s as simple as blitzing 150g oats on speed 9 for 20 seconds. Scrape down. Repeat. You want this to be a fine powder consistency. You can do more if desired. Just blitz for a little longer. 
Store in an airtight container.
To use, mix with some boiling water. You can flavour it with milk, formula or fruit purée.