The Oxford comma is an option. It is said to be helpful in situations where ambiguity is possible, e.g.
I love my parents, Donald Trump and Deputy Dawg.
An unworldly reader (or a Martian, or an AI) might possibly suppose that I meant to write that those are my parents. However, grammarians dislike ambiguity, and we can probably imagine examples where common sense does not immediately resolve any initial ambiguity of meaning. I would think that in the context of breakfast, "toast and orange juice" would resolve in a reader's mind into "some toast on a plate" and "orange juice in a glass", and not some composite edible/drinkable soggy mess. When speaking aloud, there are no commas, Oxford, or otherwise, and you would surely not expect a listener to be confused.
If you are writing for publication, you should probably be using a style guide. Here is a list of some common style guides you could use while writing:
Associated Press Style (AP) does not use the Oxford comma.
American Psychological Association Style (APA) does use the Oxford comma.
Chicago Manual of Style (CMS) does use the Oxford comma.
The Modern Languages Association (MLA) does use the Oxford comma.
The Oxford University Press (OUP) does use the Oxford comma.