In medium skillet, heat oil over medium-high heat. Add spinach, garlic and pepper flakes; salt and pepper to taste. Sauté until spinach is softened and moisture is evaporated (2-3 minutes).
Add chicken, sun-dried tomatoes and ½ cup pasta sauce; heat through. Pour remaining pasta sauce in the bottom of a 13x9-inch baking pan.
Divide chicken mixture among mushroom caps. Dollop with goat cheese and place stuffed mushrooms over pasta sauce in pan. Sprinkle mushrooms with bread crumbs; spray bread crumbs with liberal amount of cooking spray. Bake in a preheated 400°F oven until mushrooms are tender and cheese is bubbling (about 20 minutes).