Step 1

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

Step 2

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 water and transfer spaghetti to the prepared baking dish.

Step 3

Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease.

Step 4

Whisk milk and egg together in a bowl; pour over spaghetti. Add pasta sauce, diced tomatoes, garlic powder, and oregano to spaghetti and mix well.

Step 5

Spread ground beef over spaghetti mixture and top with 1/2 of the pepperoni. Sprinkle Italian cheese blend over pepperoni and top with the remaining pepperoni and Parmesan cheese.

Step 6

Bake in the preheated oven until cheese is browned and bubbling, about 30 minutes.