On the PIT-IAH segment, I would expect a muffin/pastry/bagel with drinks.

On IAH-ACA and IAH-DCA, you can expect a cold sandwich (turkey/ham) with chips and a chocolate. Maybe a piece of fruit or carrots, too.

If you order a veggie meal you'll probably get a veggie burrito that you'll have to ask the FAs to heat up for you - unless you like them frozen. Just be sure to order at least 24hrs in advance of your flight.