Mean.io Fetch all accounts for a given user on login

I have two models, User and Account. When a user signs up, an account is automatically generated for him and he becomes the owner of that account like so:

Account model

{
    "_id" : ObjectId("54f3391c96bfc9fb0b46f088"),
    "account" : "Company Name",
    "auth_token" : "test auth token",
    "owner" : ObjectId("54f3391c96bfc9fb0b46f087"),
    "users" : [ 
        ObjectId("54f3391c96bfc9fb0b46f087")
    ],
    "__v" : 0
}

Users can also be assigned to other accounts, this is saved in the users attribute for the account, Users and owner are subdocuments.

Now I would like to ensure that when a user logs in, I fetch a list of all the accounts accessible by that user, so that I can build a UI for switching account.

I have not idea how to approach the issue, any help would be appreciated!