Cut chicken in half, separating thigh and drumstick. Place in large bowl: oil, seasoning, and chicken; toss to coat (wash hands). Preheat large, nonstick sauté pan on medium-high 1–2 minutes.
Place chicken in pan, skin-side down; cook 3–4 minutes on each side or until browned. Transfer chicken to slow cooker.
Add onions and peppers to sauté pan; cook 4–5 minutes, stirring occasionally, or until vegetables begin to brown. Whisk broth, tomato sauce, dressing, and red pepper; stir into pan with onions and peppers until blended. Bring mixture to boil; pour over chicken. Cover slow cooker; cook on HIGH for 2 hours (or LOW for 4 hours).
Stir in pasta and olives; cover and cook 30–45 more minutes until pasta is tender and chicken pulls easily from bone. Stir in spinach. Serve.