Preheat oven to 350°F (175°C).

Thaw the frozen broccoli, carrot, and cauliflower combination.

In a large bowl, combine the thawed vegetables, cream of mushroom soup, 1/2 cup of shredded Swiss cheese, sour cream, Mother Nature's seasoning, and half of the French fried onions.

Mix all ingredients until well combined.

Pour the vegetable mixture into a 1-quart casserole dish.

Cover the casserole dish.

Bake in the preheated oven for 30 minutes, or until the vegetables are tender.

Remove the casserole dish from the oven.

Uncover the casserole dish.

Sprinkle the remaining Swiss cheese and French fried onions in diagonal rows across the top of the casserole.

Bake, uncovered, for an additional 5 minutes, or until the cheese is melted and the onions are golden brown.

Remove from oven and let cool slightly before serving.