In a screw-top jar, combine the oil, vinegar, mustard, tarragon, and salt. Cover; shake well. Set aside.
Slash fat on edges of steak at 1-inch intervals. Place steak on the unheated rack of a broiler pan. Broil 3 to 4 inches from the heat to desired doneness, turning once. (Allow 10 to 12 minutes for medium rare, 12 to 15 minutes for medium.) Cut the meat into 1-inch slices.
In a large mixing bowl, combine the beef, cauliflower, broccoli, peppers, onion, and bacon. Toss to mix well.
Shake the dressing; pour it over the beef mixture. Toss to coat. Arrange on a dinner plate over lettuce. Sprinkle with Parmesan. Makes 4 main-dish servings.