Preheat oven to 400°. In a large bowl, whisk together oil, vinegar, garlic, oregano, and red pepper. Add peppers and onions to the bowl and toss to coat in oil mixture. Pour into 9”-x-13" pan. Scatter sausage pieces on top of vegetables.
Bake until vegetables are tender and sausage is cooked through, 40 to 45 minutes.
Top with basil and serve hot.