Try this:
https://support.google.com/accounts/answer/6010255
Note that Google is making a bald-faced lie when they say it is less secure. So far, Google is the primary entity interested in OAuth for logging into an email account. To wit, they pretty much demand you use only their email clients. Awkward on the desktop...
I sincerely wonder if Google is going to start requiring you to type in an OAuth token when you try logging in via the browser.

Bad move, Google.