Brush both sides of each bread slice with some oil. Cut enough 1/4-inch-thick slices from feta to cover 2 slices of bread and cut tomato into 1/4-inch-thick slices. Assemble 2 sandwiches with feta and tomato slices, seasoning filling with oregano and LOTS of pepper.
In a 12-inch nonstick skillet heat 1 tablespoon oil over moderate heat until hot but not smoking and cook sandwiches until golden, about 2 minutes on each side.
Variation: Adding sliced or chopped Kalamata olives is a delicious addition.
Note: This is a grilled sandwich that is delicious served at room temperature too.