If you can use the oven when you arrive at your destination, you could do up a lasagna, freeze it, and cook it when you get there.
Not sure if this would work but you could assemble everything for a hearty stew or chili in a crock pot. When you get to the hotel on the first night, plug it in (if it is allowed) and let it cook. In the morning, wrap it well in a blanket and, assuming you don't have another 12 hours on the road, it should keep.
Hearty Salad:
I marinate some steamed & raw veggies like broccoli, asparagus, red pepper, etc in balsamic vinegar, horseradish mustard and minced garlic.
In another container, have clean lettuce, spinach, roasted corn and grated carrots.
Have separate containers for chopped tomatoes and cukes plus anything else you like in your salad.
In addition, I either put cold rice, couscous, quinoa or cold, roasted potatoes in my salad when it is going to be my main meal.
All of those things can be carried in a cooler and just dumped into a big bowl when you are ready to eat. The marinade from the steamed veggies is usually enough to coat the salad. I have filled up many times on this type of salad.