Preheat oven to 350 degrees F.
In a saucepan, heat 2 tablespoons of the oil. When the oil is hot, add the onions. Season with salt and pepper. Sauté for 1 minute. Add the peppers and garlic. Season lightly with salt and pepper. Sauté for 1 minute. Add the remaining 2 tablespoons oil and the flour, cook for 1 minute. Add the milk and 1 cup of the stock, and bring to a boil. Reduce the heat to a simmer and cook for 6 minutes. Remove from the heat. Using a hand-held blender or food processor, puree until smooth. Add a bit more stock as necessary to correct sauce thickness. Season with salt and pepper. Set aside and keep warm.
In a large bowl, combine the pasta, Monterey Jack, Cheddar and red pepper sauce, stirring to combine. Spray a 9-by-12-inch glass baking dish with vegetable spray. Pour in the mac and cheese.
Combine the Parmesan and the breadcrumbs. Top mac and cheese with a generous sprinkle of Parmesan topping. Place into the oven and cook until the mixture is heated through and the cheese is lightly browned, about 15 minutes.
Yield: 12 portions