Heat olive oil in a large nonstick skillet coated with cooking spray over medium-high heat. Add sliced mushrooms and bell pepper; sauté 4 minutes. Add minced garlic, and sauté 30 seconds. Add Caramelized Onions, chicken broth, salt, black pepper, and red pepper; bring to a simmer. Remove from heat; stir in sour cream and oregano. Serve over pasta, and garnish with oregano sprigs, if desired.