This works fine if you have the vegetables on you and not requesting items from other toons. It will buy the supplies to make vegetables. I am saying that in batch mode when you request items to make Vegetable Oil it is looking for Lettuce, Carrots and Turnips when the tradeskill Mule has Vegetables.
Not that it matters since you would have to navigate to western waste tov to get vegetables. but they are free on a merchant there, thus making it a vendor bought item to eliminate having to make vegetables.