1Heat oven to 350°F. Grease bottom and sides of 8-inch square (2-quart) glass baking dish with shortening.
2In medium bowl, stir Bisquick mix, milk, mustard and egg until blended. Pour half of batter into baking dish. Top evenly with half of the roast beef and 1/2 cup of the cheese. Top with remaining roast beef. Pour remaining batter over roast beef.
3Bake uncovered 45 to 50 minutes or until golden brown and center is set. Sprinkle with remaining 1/2 cup cheese and the pepper. Let stand 5 minutes before serving.