Place the chicken thighs in the bottom of the slow cooker in a single layer.
Add the sliced bell peppers, mushrooms, onion, and garlic on top of the chicken.
Pour the crushed tomatoes and chicken broth over the vegetables.
Sprinkle the oregano, basil, salt, and pepper evenly across the top.
Cover the slow cooker and cook on low for 6 to 8 hours until the chicken is very tender.
Stir gently once or twice if possible during the last hour.
Sprinkle with fresh parsley before serving.