Vegetarian items that are filling and also work for someone doing that much cardio: pastas, rice, corn, tofu, dried tofu, bean thread (noodles made from various vegetables like mung bean, yam, cassava or canna starch), mushrooms (also good for umami).
I find vegetarian Thai spring rolls to be quite filling and can be served cold. Rice wrappers filled with bean thread noodles, shredded carrots, asparagus, julienne red pepper, shredded daikon, chiffonade of basil, plus a dash of fish sauce (optional). Can be served with a peanut sauce (optional). If you want, you can blanche the veggies, but do not need to. I usually put shrimp in, but you can add dried tofu or just serve without any protein.