Preheat oven to 375°F (190°C).
Pat the chicken dry with paper towels and season with oregano, Italian seasoning, salt, and black pepper.
Heat olive oil in a large oven-safe skillet over medium-high heat.
Place the chicken skin-side down and cook for 6–7 minutes until golden brown. Flip and cook for another 3 minutes. Transfer to a plate.
Add the Italian sausage to the same skillet and brown on all sides. Remove and slice into large pieces.
Add the sliced onion and bell pepper to the skillet. Cook for about 5 minutes until softened.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the white wine and scrape the bottom of the pan to loosen the browned bits.
Add the chicken broth, white wine vinegar, lemon juice, and crushed red pepper flakes (if using). Bring to a gentle simmer.
Return the chicken and sliced sausage to the skillet, nestling them into the sauce.
Transfer the skillet to the oven and bake for 25–30 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Garnish with fresh parsley and Parmesan cheese if desired.
Serve hot with crusty bread, pasta, mashed potatoes, or roasted vegetables.