You're in luck - the New England Culinary Institute is based here. They operate a working restaurant located on the same street as the state capital. Lunch prices are very reasonable for food and atmosphere but there's no telling what is offered on a particular day.
Check will run around $30. A local I do business with recommends Sarducci's but I cannot vouch. Montpelier is much smaller in size than you'd expect.
re: Ken Bozek
I am in Montpelier at least 3-4 times a year on business The town is quite small, and I find myself driving to Burlington most times. Waterbury a few exits down is far more interesting meal wise
NECI is fine. Since it is a school, I find it can be uneven at times. But there is always quite a varied selection of things to try. La Brioche serves pretty good pastries and Main street grill is where I usually eat I was not as impressed with their "upscale" place - Chef's table.
Sarducci's is right down the block and is very good Italian with brick oven pizza. Horn of the moon was much better awhile back, I have been disappointed with the changes made to their menu and while their cookbook is good, found the restaurant had gone downhill . Maybe it's changed. Sometimes I drive over to the wayside on the Barre road, decent friendly diner.
Bear in mind, all these places are within 2-3 min walk of each other. The main business "district" is only a few blocks long-Main & State Street.
Hope this helps