Heat oil in a large non-stick skillet over medium high heat. When oil is hot, add chicken sausage and cook for 1-2 minutes per side, until golden.
Reduce heat to medium, and add onion, bell peppers, and garlic to skillet and cook another 4-6 minutes, until peppers are tender and onions are translucent.
Season with salt and pepper to taste and sprinkle with grated parmesan.