In Cookwise, Shirley Corriher suggests comparing the effects of oil on one
lettuce leaf and vinegar on another. I tried it: with oil the lettuce leaf
wilts some; with vinegar, not at all. Before the experiment, I had always
thought that oil "protected" the greens.
For tabouli I love the fresh taste and light texture when no oil or oil
substitutes are added. I use lots of curly parsley (about 2 cups chopped)
in a recipe similar to Susan's, and the juice from the lemon and fresh
tomatoes combine with the mint to make a most refreshing and tasty salad.
It never fails to get rave reviews at potluck meals.
Omitting the oil entirely and letting the herbs and fruit juice or vinegar
rule seems to work well with most salads in which greens or beans are the
major ingredient. With grains, it's a little more iffy. However, it's a lot
easier to add an oil substitute (if leaving it out doesn't work) than it is
to remove it. :-)