Heat the oven to 400°F. Bring a covered saucepan of water to a boil for the green beans.
Slice or pound the chicken to roughly 1/2-inch thickness, making four portions. Season with Italian seasoning, garlic powder, salt and pepper.
Heat the oil in a large oven-safe skillet over medium heat. Cook chicken 3–4 minutes per side until lightly browned.
Spoon marinara evenly over the chicken. Top with mozzarella and Parmesan. Transfer the skillet to the oven, or move everything to an oven-safe baking dish. Bake for 8–12 minutes, until the thickest part of every piece reaches 165°F and the cheese melts. Timing depends on thickness.
While the chicken bakes, boil the green beans for 4–6 minutes until tender to your liking; drain. Divide the chicken, sauce, cheese and beans evenly among four plates.