I worked at McDonald's frying French Fries for one night as part of a school fundraiser. The ingredients were listed on the box and included "flavoring extract (beef origin)". Mmmm beefy-goodness....
Edit:
I looked up the ingredients, they have changed the wording a little but they still add beef flavor to their fries.
FRENCH FRIES:
Ingredients: Potatoes, Vegetable Oil (Canola Oil, Soybean Oil, Hydrogenated Soybean Oil, Natural Beef Flavor [Wheat and Milk Derivatives]*, Citric Acid [Preservative]), Dextrose, Sodium Acid Pyrophosphate (Maintain Color), Salt.
Prepared in Vegetable Oil (Canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil with TBHQ and Citric Acid added to preserve freshness), Dimethylpolysiloxane added as an antifoaming agent.