You were asking for filling food that Q could eat a lot of...
now I don't know if Q is a picky eater, but the following works great for husband, who is a big guy, goes to the gym, is hungry all the time, but doesn't want to get heavy:
Fiber and protein keep you full longer, so I buy these microwaveable packets of brown rice by Uncle Ben's (90 seconds in microwave), or Quinoa (pronounced keen-wa) which is a high fiber grain like rice, the brand is Seeds of Change, sold in the rice section of the supermarket, also 90 seconds in microwave. I mix that with broccoli (high fiber also) and make a huge plate for him. Low calorie, but very filling. I stir fry the broccoli with-garlic and oil for a little bit, and put some grated parmesan cheese on top, mix in the rice or quinoa and that's a gigantic side dish. Whole wheat pasta with- broccoli is great with just olive oil and garlic. Spinach has more protein than steak. Rice and beans is filling and not expensive. Bananas, too.