Sprinkle beef cubes with salt and pepper. In 10-inch skillet, heat oil and garlic over medium-high heat, stirring frequently, until garlic is toasted (be careful not to burn garlic). Remove as much garlic as possible from skillet; discard.
Add beef cubes to skillet. Cook 4 to 5 minutes, stirring occasionally, until brown on all sides and desired doneness; drain.
Meanwhile, in small bowl, mix mayonnaise, sour cream, tomatoes and horseradish. Spoon beef cubes into serving bowl or onto platter; sprinkle with parsley. Serve with toothpicks for dipping into sauce.