Preheat the oven: Preheat your oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish or casserole dish with cooking spray or butter.

Mix the casserole base: In a large mixing bowl, combine the condensed cream of chicken soup, sour cream, chicken broth, minced garlic, salt, pepper, and oregano.

Add the vegetables: Fold in the thawed California vegetables, ensuring they are evenly coated with the creamy mixture.

Layer the casserole: Pour the vegetable mixture into the prepared baking dish and spread it out evenly. Sprinkle the shredded Monterey Jack cheese evenly over the top of the casserole.

Bake the casserole: Place the casserole in the preheated oven and bake for 25-30 minutes, or until the cheese is fully melted and the edges are bubbling.

Add the topping: After the casserole has baked for 25-30 minutes, remove it from the oven and sprinkle the French fried onions evenly over the top. Place the casserole back in the oven and continue baking for another 5-10 minutes, or until the onions are crunchy and have turned a golden brown color.

Serve and enjoy: Take the casserole out of the oven and allow it to sit for a few minutes to cool slightly before serving. This dish pairs well with roasted meats, grilled chicken, or can be enjoyed as a main course on its own.