Bring a large pot of lightly salted water to a boil. Add penne pasta and cook for 8 to 10 minutes or until al dente; drain.
In a large skillet over medium heat, cook the sausage until evenly brown. Remove from skillet and set aside.
Melt butter in the same skillet over medium heat. Stir in garlic, oregano, and pepper. Gradually blend in flour to form a roux. Slowly stir in milk, stirring constantly until mixture thickens.
Stir in sausage and cooked pasta. Simmer 5 minutes before serving.