Pat the chicken breasts dry with paper towels. If they are very thick, you can pound them slightly to an even thickness for more even cooking.
In a small bowl, mix the olive oil, salt, and pepper.
Brush the olive oil mixture all over the chicken breasts.
Place the chicken breasts in a baking dish.
Spoon the marinara sauce evenly over each chicken breast.
Sprinkle the mozzarella cheese and Parmesan cheese over the sauce.
Sprinkle with dried oregano.
Bake for 20-25 minutes, or until the chicken is cooked through (internal temperature reaches 165°F or 74°C) and the cheese is melted and lightly golden.
Let it rest for a few minutes before serving.
Notes
Serve with your favorite pasta, a side salad, or steamed vegetables for a complete meal.