I haven't done this with onions but I have with leeks. When I have bought too many, I finely chop them and then freeze in bags. Then, when I am doing a soup, I just get the bag out of the freezer and put them straight in the pan and there is no difference with the finished soup.

I think if you read the info on websites about this they tell you to cook first but I dont and all is well

You can buy frozen (uncooked) onoins in TEsco so I think they'll probably be fine.

i've never tried doing them raw but my mum fries them first and then freezes them. think it works fine for her

I have just ordered a chopper from Pampered Chef to finely chop onions (and other things)and because it's quite a task to clean, I thought I would chop a few onions at a time and then put them into bags an pop them into the freezer. Does this work? Do you need to defrost or could they go into spag bol/ casserole from frozen? Thanks