Hi @jaylee78,

I don’t think you will be able to track method level grants through History log. Probably for the best as these are tracked through base security sys tables and can become a massive overhead if logging is setup on those. 

You could try out a custom event (PRES_OBJECT_GRANT_TAB) for this matter since it records old value and new value.  You can just record these values along with the session user and timestamp to a table you created. Once again, be vary on the overhead if you are doing lot of changes to security.

Hope this works.

Regards,
Charana