In small bowl, mix chili powder, oregano, cumin and salt. Rub mixture on both sides of beef. Let stand 10 minutes at room temperature.
Set oven control to broil. Place beef on rack in broiler pan. Broil with top 3 to 4 inches from heat about 10 minutes for medium doneness, turning once, or until desired doneness. Cut into 1/8-inch slices.
Warm tortillas as directed on package. In small bowl, mix sour cream and horseradish. Spread 3 tablespoons horseradish mixture over each tortilla; top each with 1 cup of the lettuce and 1/4 cup of the tomato. Top with beef. Wrap tortillas around filling.