Veiled chameleons are considered insectivores, which means their diet consists of insects and bugs. Although I have heard of them eating small lizards and other small vertebrates, I would suggest against feeding yours anything with bones because it risks impaction (when the reptile can't digest something and it blocks their digestive system).
I have also heard of some older chameleons eating leafy greens, so if you want to try that you could. I would stick to the more nutrient rich greens though, something like kale. it's also a good idea to break it up a bit before feeding them, as reptiles don't really chew so much as mash their food.
Like John said, you're much better off gut loading your insects to make sure they have all the nutrients you want your chameleons to receive. More so, I would suggest using vegetables more than fruits, as they're higher in nutrients, with the exception of squash which are also good and are technically fruits. You can also feed them a pre-made formula if you want to take some of the scheduling out of it, like Fluker's Orange Cubes I use for crickets.
Something else you can do is dust the insects with calcium powder at a couple mealtimes a week. Generally dusting insects is used to compliment gut loading them, as dusting provides more calcium than gut loading would, and gut loading provides more vitamins. It's more important when the chameleons are younger as it helps with their growth and development. Older chameleons don't need calcium dust much more than once a week, maybe even less.
Some good staple insects to feed them are: crickets, mealworms, dubia roaches, silkworms, and praying mantises.
Other insects you can feed them, but maybe more so as a treat are: waxworms, moths, and I've heard small stick insects.