It's Izzys time of year...

From what I've seen, eating veggies is either a behavior they pick up from other dogs, or by eating veggies that are prepared with stuff they like. Over time they come to understand that this is "food."

Corn on cob with butter on it would be enough to get a dog started.

Carrots cooked in broth might work. Once they're accepted, then switching to raw could work.