In a blender or food processor, combine the ricotta with the oregano, salt, and pepper. Process to blend.

Rub the chicken with the garlic powder.

Heat the oil in a large skillet over medium-high heat. Add the chicken and cook for 12 minutes per side.

Place the chicken breasts, side by side, in a large baking dish and allow to cool.

Preheat oven to 350°

Spoon 1/4 cup of the cheese mixture and 1/4 cup tomatoes onto each chicken breast. Top each chicken breast with 1 slice mozzarella.

Bake for 20 minutes, or until a thermometer inserted in the thickest portion of a breast registers 170° F (75° C) and the juices run clear.