I should have done this in the first place. I searched the MSDN KB using the keywork Oracle and found the following in article Q149882. The syntax is to enclose the call in curly braces.

h=SQLConnect("ORADSN","USERID","PWD")   && Establish a connection
IF h > 0
   WAIT WINDOW "Connection Successful" NOWAIT
   =SQLExec(h,"{Call SP_MYPROC}")       && Execute the stored procedure
   =SQLDisconnect(h)                    && Terminate the connection
ELSE
   WAIT WINDOW "Connection Failed"
ENDIF