The last time I made stew I used red wine and parsley for flavour and left out the onion entirely, which seemed to help. It's not quite the same but it's still tasty.I have learned to use a lot less onion in my stews. It doesn't take much for flavour. 1 onion is actually enough for a week of stews.
Onions can be hard on the digestive system.
I used to have a lot more gas when I ate a lot more onions.