Spaghetti Bake

Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.

Bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally, until cooked through but firm to the bite, about 12 minutes. Drain.

Heat a large skillet over medium heat; cook and stir onion and bell pepper until tender, about 5 minutes. Transfer vegetables to a large bowl. Return skillet to stove top and increase heat to medium-high. Cook and stir ground beef in skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease. Transfer beef to the same bowl as the vegetables.

Stir spaghetti, spaghetti sauce, Cheddar cheese, cream of mushroom soup, mushrooms, olives, oregano, and sugar into beef mixture. Pour spaghetti mixture into prepared baking dish and sprinkle with mozzarella cheese and Parmesan cheese.

Bake in preheated oven until bubbly and hot, about 45 minutes.