This source says that 80mg of oxycodone in the body should be enough to cause an overdose. I would bring it up to 100mg to be safe. However, this is more than likely data pertaining to
intravenous oxycodone, not oral. The oral bioavailability is anywhere from 60-87% so I would go for the worst-case scenario and ingest 170mg of oxycodone to achieve overdose. Maybe 200 if you want to be on the safe side.
However, this is in an isolated study without potentiators like alcohols, benzos, etc. If you ingested these as well, alongside an antiemetic to reduce vomiting, I wouldn't be surprised if you overdosed on even lower doses, although I wouldn't risk anything but the guaranteed amount.
Please take these calculations with a huge pile of salt. I am simply basing my findings off of Google, which already made it hard enough to find information on opiod lethality, let alone that of oxycodone. There's also a lot of information online that points to it being lower as well as higher, such as the LD50 in mice being something insane like 450mg/kg. This is almost definitely not how much you need to CTB as a human; I would expect that 450mg alone would kill you, let alone that much times your body weight. 200mg is the most accurate estimate I can make given limited data