I am assuming that you will be in OHare. Three hours is not a lot of time to exit the airport, go to a restaurant, dine and return in time for the long security lines. Four hours is more do-able. I do not recommend the Marriott hotel restaurant. In my humble opinion, the best selection for food is in Terminal 1-the United terminal. You can reach it by the 'people mover'. In terminal one there are two sections-B and C. There is a gross Chilis in B. Proceed to C. I recommend the Bergoff restaurant for a tasty fresh cut roast beef, ham, pork or corned beef sandwich on delicious rye bread. Or you can have a brat. The Berghoff beer on tap (lager or dark) is always fresh. Or you can proceed into the food court and go to Billy Goats. The place is famous (Cheezeborger-pepsi- chips). The hamburgers are flavorless, thin and undersized compared to the kaiser bun. Do not buy these. So I opt for the ribeye steak sandwich. For the price ($5.00) it is better than the Panda, California Pizza Kitchen, Spago salads/pizza and Mc. Donalds that are also available. Terminal 2 has a cafeteria type place if you want to eat institutional food. The international terminal 2nd floor before security has a Gold Coast Dogs that serves char burgers, hot dogs, italian sausage/beef sandwiches.