Rocky Mountain oysters are bull testicles. They are often deep-fried after being peeled. Sometimes they are pounded flat. Considered a delicacy, they are most often served as an appetizer with a cocktail sauce dip. "Fries" as they are known in Oklahoma and North Texas are a well-known novelty dish in parts of America and Canada where cattle ranching is prevalent. No matter what they are called, they are most commonly served at festivals, such as the ones in Virginia City, Nevada, Montana and Phoenix, Arizona, amongst ranching families, or at certain specialty eating establishments and saloons. U.S. raised grass-fed beef.