As a relative newbie myself, I don't have a specific recommendation for
an oak finish without a stain, but I've had good luck with polyurethane
gel from Rockler over stains, and over unstained birch ply. It was
easy to use, and I found it emphasized the grain of the birch ply
without noticably changing the color. (Remember to sand lightly
between coats, because oil-based polyurethane can't bind to itself.) I
just finished a spice rack of red oak, and I found a light-colored
pigment stain emphasized the grain and really brought out more color of
the wood, without making it look artificial or anything.
Overall finishing recommendation: I have Flexner's finishing book, and
I highly recommend it - it is very helpful for understanding what's
actually going on with several different kinds of stains and finishes.
Good luck with your project!