The Oxford Comma

I've been using the Oxford comma for years and never knew it had a name. For those who may not already know what that means, it is the comma that appears after the last word in a grouping. For example: I ate cookies, drank milk, cleaned up, and left the kitchen. Many writers do not use a comma after the last word and apparently it's OK. The important thing is to be consistent in your writing. It makes more sense to me to use the comma in such a grouping. Now I know there's a name for it!