I have used oil pastels on gesso primed masonite panel (smooth side), with good success sprayed with matte medium when finished. You can use turps as a medium with the oil pastel. You might try doing some testing on the type of wood you plan to use. Also, make sure you use a good brand of artist oil pastel. Most if not all oil pastels are uv protected. Even so, wouldn't use them with the thought of an out door piece or display in direction sunlight.
Check the manufacturer's notes on the brand you plan to use.
I'm including a piece I did using the Pastel Pencils
Kathy

Oil Pastel Pencil on non-primed basswood