What is stronger morphine er or oxyicodone?

It depends on which list you read. Some believe the two to be equal in potency. Others believe oxycodone to be about 50% stronger than morphine when taken orally. I tend to go with the 50% stronger group as I've used both and find oxycodone to be stronger. The same holds true for whether the formulation is short acting or extended release.

If used IV they are about equal in potency. IV is always short acting.

BY IV morphine is stronger but when taken orally the bioavailability of morphine is only about 35% where oxycodone is between 60 and 85%. So oxycodone is stronger in pill form but morphine is stronger IV'ed