1. Place cheese and sour cream in food processor bowl. Cover; process until smooth. Transfer to small bowl. Cover and refrigerate.
2. Place onion and bell pepper on grid over medium, ash-covered coals. Grill, uncovered, 10 to 12 minutes or until bell pepper is slightly blackened and onion is tender, turning once. Set onion aside. Place bell pepper in plastic bag and close. Let stand until skin is loosened.
3. Place bread slices on grid over medium. Grill, uncovered for 3 minutes, turning once.
4. Place beefsteak on grid over medium. Grill uncovered for 13 to 16 minutes for medium- rare to medium-doneness, turning occasionally. Season with salt and pepper as desired, keep warm.
5. Meanwhile, remove skin from bell pepper. Coarsely chop bell pepper and onion; place in medium bowl. Add tomatoes, basil, olives, oil, vinegar, garlic, salt, pepper and mix well.
6. Carve steak into 32 slices. Divide cheese mixture equally among 32 bread slices, spread evenly. Top each bread slice with 1 steak slice and 1 tablespoon of tomato mixture.