Have not tried this because I don't yet have a stored proc.
However, I have heard some people say it can't be done.

What I'd like to do is call an Oracle stored procedure since
it should run faster on the server. Also, the code involved
will probably exceed that which should be used in SPT. For
instance, I need to do several joins from intermediate result
sets. Can I get the results of the last query from the stored
proc returned when invoked as a STP call? If so, what is the
syntax?