Mix oil and crushed garlic in a large skillet and heat over low heat for 1-2 minutes, or just until fragrant.
Saute chicken breasts in the oil for approximately 20 minutes, or until cooked through (flipping halfway through cooking).
Place cooked chicken in a greased casserole dish.
Cover chicken with marinara sauce, sprinkle with basil, top with half of the mozzarella, half of the Parmesan, and the crushed croutons. Sprinkle with remaining cheeses.
Bake in a 350 degree oven for approximately 25-30 minutes, or until cheese is melted and brown on top and dish is heated through.