I made quinoa salad for this bento. There are several different varieties of quinoa, which you may know about. I took a picture of the four that I happen to have in my pantry right now: clockwise from top left. Black, regular, red (Peruvian) and tricolor (which is just obviously the previous 3 kinds, already mixed together).
This time I used tricolor quinoa. It's so easy: just saute the veggies first (I used yellow capsicum, onion, garlic, carrots, zucchini), then add the quinoa and broth in a 1:2 ratio. It cooks in 15 minutes. After taking off heat, stir in diced celery, spring onion and almonds for crunch. Use your favorite flavorings: I used garlic powder and cumin this time and it was pretty good. This meal is healthy and tastes good at any temperature; even as a cold salad, making it perfect for bento. Quinoa is also a "perfect" protein, as it contains essential amino acids and yet is a (plant) grain. Plus, it's quick and easy to prepare. It's also good mixed in with oatmeal or other hot cooked cereal for breakfast.
In addition, he gets carrots, grape tomatoes, romanesco, and a cucumber frog. For fruit he has cherries, kiwi flowers and sliced kumquats. Ribbit!