Preheat oven to 350. Cook pasta 2 min less than package directions, or follow "al dente" directions.
Heat 3 tsp olive oil in a large pot over medium heat. Add chicken in batches and cook until no longer pink. Remove from pan. In same pan, cook mushrooms 3 - 5 min or until tender.
Add garlic, and cook 1 min longer. Add soup, chicken broth, 1 cup of the cheese, oregano and pepper. Add spinach and tomatoes. Return chicken to pan.
Drain pasta, add to soup mixture.
Directions say divide between two 8 in square baking dishes, but I plan on using a 13 x 9 in pan. Sprinkle with remaining cheese. Bake covered for 15 - 20 minute
Freezing Directions:Cool unbaked casseroles and freeze. To cook, thaw in refrigerator overnight. Remove from refrigerator 30 minutes before baking. Bake covered at 350 for 1 1/4 hours or until 165 degrees in the center.