My guy eats grass to induce vomiting if he has a queasy stomach, and in the spring he seems to like to graze on the fresh spring grass. I discourage the practice as much as I can, because it is likely to result in vomiting if he gets too much. Interestingly, I have not yet had a Basenji that likes lettuce, although all of mine have enjoyed broccoli, green peppers, asparagus and a number of other vegetables. My current boy doesn't like green beans, but my previous dogs all did.
"In order to get along with a Basenji, you have to be at least half as smart as the dog!"