How to make these meatballs gluten free?

I'm making Gordon Ramsay's Meatballs on Sunday for my family, but my mum can't eat gluten.Here is the original recipe:500g of minced beef75g of breadcrumbs3-4 tbsp milk1 onion, 2 garlic cloves, salt, pepper, chilli flakesI was thinking about switching from breadcrumbs to ground oats so my question is how much should I use.Important thing is that I will also double the recipe (I mean I will use 1kg of meat).If you have any other ideas on how can I make them gluten free please share them with me (excluding gluten-free breadcrumbs). via /r/AskCulinary http://ift.tt/2FVVGMf