Heat oven to 350°F. Place bread slices on ungreased cookie sheet; brush lightly with oil. Bake at 350°F. for 8 to 10 minutes or until crisp. Cool 5 minutes or until completely cooled.
Meanwhile, in small bowl, combine mayonnaise, cheese, 2 tablespoons chives, the capers and garlic powder; mix well.
Spread about 1/2 tablespoon mayonnaise mixture on each toasted bread slice. Top each with roast beef and tomato slice. Garnish with chives.