you would put the Oxford comma before the conjunction that concludes the list. It doesn't matter if the conjunction is "and" or "or," the Oxford comma would come directly before it. That's if you ...

When listing only two items or things, it is not necessary to put a comma before the word ‘and’. Commas can be categorised as bracketing, joining, listing or gapping commas. Bracketing commas ...

An Oxford, or serial, comma is the last comma in a list; it goes before the word "and ... three sentence arguments in existence for the use of the Oxford comma: It's likely the book is dedicated ...