Check out this link for creating a linked server:
http://technet.microsoft.com/en-us/library/ms190479.aspx.
There is an example specific to Oracle. You will need to make sure the appropriate provider from Microsoft, and possibly Oracle are installed first.
I had to do this for a demo a little over a year ago. It took a couple tries to get it right, but it did work. Unfortunately, I no longer have access to the details.