I doubt they would go after a bowl of green in the cage, however if you have a ficus or other plant I am sure you will see bites taken out of it when they are hungry and you dont bugs in the cage. I believe this to be good enough, however others may say different.
You can try greens (dandelion greens, collards, kale, endive, ROMAINE lettuce (not lots of this one though), mustard greens, etc.) and veggies (sweet red pepper, squash, carrot, zucchini, sweet potato, etc...all diced to appropriate sized pieces or slivered for firm/hard ones) and a bit of fruit (apple, pear, melon, berries, etc. cut to appropriate sizes).
Many won't start to eat the above until they are about 6 months old...but there are exceptions. If the crickets are free-ranged, it helps to keep them fed even if the chameleons don't eat these things.