The benzo(xanax) would cause more of a concern than the opiate(oxy) but like others have stated it really depends on you. If it were me I'd just take the oxy during the day, maybe just one if I had little to no tolerance. Save the xanax for night time when you have the time to sleep it off. Like I've always heard from the wise older heads.. Remember you can always do more if you don't get the desired effect, you can't get less dead. Basically just ease into it, don't swallow everything you have just because you think it will be a more enjoyable high. In all honesty the xanax will be the only thing you feel, and it will just knock you out. Why not save the oxy for tomorrow, taken by itself can be really euphoric.