Will oxycodone and morphine show up the same in a urine test?

Honestly, Yes & NO

Oxycodone usually does not come up positive for morphine on a drug test because they have different chemical structures...They are almost identical, so it really depends on the amount that was ingested...A faint line may appear for morphine meaning that the urine is skeptical, but nowdays urine is being sent to labs to confirm a specific drug or drug metabolite...Example : Oxycodone metabolizes in the body as Oxymorphone,, meaning if a GC/MS (Gas Chromatography/Mass Spectrometry) test is called upon, science can detect if a person has used oxycodone...But nowadays they have a sepcific dipstick/cup test for oxycodone , so i wouldn't suggest to continue using oxycodone if you are not prescribed, especially if you have legal problems where you are being drug tested.

This is a very, very accurate answer, hope i helped you solve your issue