Preheat the oven to 350 degrees F (175 degrees C).
Heat 2 teaspoons oil in a saute pan over medium heat. Cook and stir sausage until browned and crumbly, 5 to 7 minutes. Drain on a paper towel-lined plate.
Add remaining 2 teaspoons oil to the same pan. Saute onion, pepper, and garlic until onion is translucent, about 5 minutes. Stir in cooked sausage. Add cream cheese, marinara sauce, and Italian seasoning. Mix all together.
Pour mixture into a baking dish. Top with mozzarella cheese and Parmesan cheese.
Bake in the preheated oven until cheeses melt and start to brown, 25 to 30 minutes.
