Not all oak is equal. Flat sawn red oak, the cheapest and most common oak, doesn't engrave well due to the variation in the grain. Quarter sawn oak, red or white engraves uniformly and will produce pleasing results, particularly if color filled.

Julian's example appears top be quarter sawn white oak.

I would not use stains for color filling as it is very difficult to avoid the capillary action (bleeding) as previously mentioned.