WHY I USE THE OXFORD (OR SERIAL) COMMA

WITH:

After winning the Academy Award, Matthew McConaughey thanked his parents, Jennifer Garner, and Jared Leto.

WITHOUT:

After winning the Academy Award, Matthew McConaughey thanked his parents, Jennifer Garner and Jared Leto.

Without the comma we have a false appositive.

WITHOUT:

Mary was proud of her recipes for cupcakes: marzipan, almond and coconut and chocolate chip.

(Is it almond and coconut or is it coconut and chocolate chip or are all three combined?)

Book dedication: To my parents, Ayn Rand and God.

The writer is a demigod with an inherited tin ear for language?

Since you have to use it in some cases to prevent confusion, be consistent, and use it always.