View source for Is a comma really necessary after the last element in a list of three or more?

Technically, using a comma after the last element in a list of three or more is not necessary. However, it does help to ensure that the last two items in the list are not misinterpreted. 

Consider these examples:

: Uncle Charlie wanted me to pick up some bread, eggs, macaroni, and cheese.
: Uncle Charlie wanted me to pick up some bread, eggs, macaroni and cheese.

The last sentence would not be grammatically correct if the desired item was macaroni and cheese due to the lack of a conjunction before the word macaroni. Yet, seeing these two words placed together in this manner would cause someone to question the meaning. According to Aaron, adding a final comma in a list "is never wrong, and it always helps the reader see the last two items as separate".<ref>Aaron, Jane. The Little, Brown Compact Handbook With Exercises. 7th ed. New York: Longman, 2010. 310. Print. </ref>