01 -
Preheat the oven to 325°F and grease a 9x13-inch casserole dish.
02 -
Cook the spaghetti according to the instructions on the package. Once done, drain the water and set aside.
03 -
Melt butter in a large skillet over medium heat. Add the diced onion, bell pepper, and sliced mushrooms. Cook for about 5 minutes until the vegetables soften. Stir in oregano, salt, and black pepper.
04 -
Mix in the diced tomatoes and sliced black olives. Let the mixture simmer gently for about 5 minutes.
05 -
In a separate bowl, whisk together the softened cream cheese and the milk.
06 -
Remove the skillet from heat. Add the cooked spaghetti, shredded mozzarella, and the cream cheese mixture to the skillet. If the skillet is too small, transfer everything into a large mixing bowl to combine.
07 -
Transfer the combined mixture into the prepared casserole dish. Bake in the preheated oven for 40 minutes until bubbling and heated through.