Preheat the oven to 425°F (220°C).
Place the quartered baby red potatoes and trimmed green beans on a large rimmed baking sheet.
Drizzle the vegetables with 1 tablespoon avocado oil and toss with your hands to coat evenly.
Season the potatoes and green beans with 1/4 teaspoon salt and 1 tablespoon seasoned pepper, and arrange them on the baking sheet leaving a space in the center for the chicken.
Place the pounded chicken breasts in the center of the baking sheet. Drizzle with the remaining 1/2 tablespoon avocado oil and season both sides with the remaining 1/4 teaspoon salt and 1/4 teaspoon black pepper.
In a small bowl, whisk together the mayonnaise, shredded Parmesan, and Spinach & Herb Seasoning until smooth.
Spread the mayonnaise mixture in an even layer over the top of each chicken breast.
Bake for 22 to 25 minutes, or until the chicken reaches 160°F (71°C) on an instant-read thermometer and the potatoes are tender.
If desired, broil on high for 1–2 minutes to brown the topping, watching carefully to avoid burning.
Let the chicken rest for 5 minutes before serving.