Preheat the oven to 400 degrees F (200 degrees C).
Bring a large pot of lightly salted water to a boil. Add penne and cook, stirring occasionally, until tender yet firm to the bite, about 11 minutes.
Meanwhile, melt butter in a saucepan over medium heat. Stir in cream, half-and-half, and garlic salt. Add Gruyere cheese, 1/2 cup mozzarella cheese, Parmesan cheese, and Oaxaca cheese. Stir into cream until melted. Drain pasta and add to the sauce; stir to coat.
Spray a casserole dish with cooking spray and pour in pasta mixture. Sprinkle with remaining 1/2 cup mozzarella cheese.
Bake in the preheated oven until cheese is bubbly and slightly browned, 15 to 20 minutes.
