Preheat oven to 350 F.
Spray a large casserole dish with non-stick spray.
Heat oil over medium-high heat in large skillet. You need a skillet large enough to hold the meat, veggies, and pasta, so if you don't have a really large one, use a big pot instead.
Add sausage and cook until done.
Meanwhile, cook the pasta until almost done. Drain well.
Remove sausage with a slotted spoon.
Add in the peppers and onion and cook until starting to soften, 8-10 minutes.
Season with salt and pepper and add the garlic and cook another minute.
Remove from heat. Stir the meat back into the veggies.
Add the pasta to the pan and stir well.
Pour mixture into the casserole, cover with foil, and bake 35-40 minutes.
Serve drizzled with a little olive oil and sprinkled with freshly grated Parmesan cheese.