Preheat the oven to 350 degrees F.
Spray a 9x13" baking dish with cooking spray.
Cook the spaghetti according to package directions.
While the spaghetti is cooking, prepare the rest of the ingredients.
In a large skillet, heat the olive oil over medium-high heat and add the turkey, onion, and red bell pepper.
Cook, breaking up the turkey into smaller pieces as it cooks, and stirring well.
Add the taco seasoning along with ¼ cup of water, and stir well to combine, cooking until the water has thickened.
Add the corn, marinara, diced green chiles, and stir well to combine.
Add the sauce to either the large pot that the spaghetti cooked in or a large bowl with the cooked spaghetti, and stir well to combine.
Add half of the spaghetti mixture to the baking dish.
Sprinkle 1 ½ cups of the shredded cheese evenly on the spaghetti.
Top the cheese with the remaining spaghetti mixture and then sprinkle with the remaining cheese.
Bake in the preheated oven for 20-25 minutes, until the cheese is melted and the casserole is bubbling.
Note: you can also refrigerate before baking if you want to prep this ahead of time. Simply add 5-10 minutes to the baking time to account for the colder starting temp.
Serve topped with chopped green onions. Enjoy!