In a large mixing bowl, combine all vegetables, cream of mushroom, sour cream, seasonings, and 4 oz of crispy fried onions. Stir well.
Transfer mixture to a greased 9x13-inch baking dish.
Evenly sprinkle cheese over top followed by remaining crispy fried onions.
Bake for 40 minutes or until mixture is bubbling and onions are golden brown.
Notes
Draining excess liquid from veggies is important to prevent mushiness.
If you are reheating leftovers, add more crispy onions before reheating.
For a little added depth, try mixing a dash of smoked paprika or a sprinkle of Italian seasoning into the casserole before baking. A few fresh herbs like parsley or thyme on top also add a nice finish.
If you want an extra-crispy topping, broil the casserole for 1-2 minutes at the end of baking. Just keep a close eye on it to avoid burning!
This casserole can be assembled a day ahead and stored in the fridge (without the crispy topping) until you’re ready to bake. Add the topping just before baking for best results.
When reheating leftovers, add a few tablespoons of milk or cream to keep the casserole from drying out. Then cover and bake as directed.