Preheat your oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper for easy cleanup.
Arrange the sliced chicken or turkey sausage, bell peppers, and onion on the prepared baking sheet.
Drizzle with olive oil and red wine vinegar.
Sprinkle with garlic, salt, basil, oregano, black pepper, and red pepper flakes.
Toss everything together until evenly coated, then spread into a single layer.
Bake for 25–35 minutes, stirring halfway through, until the vegetables are tender and lightly caramelized.
Garnish with fresh basil, parsley, and Parmesan cheese if desired. Serve your Sausage and Peppers immediately.