Can you mix oycodone and Tylenol with codeine together?

Absolutely NOT. This is called a "duplication of therapy" and in the case of oxycodone and Tylenol with codeine, it can cause a person to stop breathing, or potentially aspirate (breathe in) their vomit during periods of unconsciousness. Only do this if a pharmacist or doctor tells you to, as they can guarantee that you will not overdose.