Preheat oven to 350° F. Spray a 9×13 pan with cooking spray and set aside.
Heat a large sauté pan to MEDIUM heat. When hot, add beef and chopped onion. Cook together for 10-12 minutes until brown. Drain any excess fat.
Add mushrooms, bell pepper, beans, tomatoes, green chilies and taco seasoning to pan. Simmer for 5 minutes.
Place half of the tortillas on the bottom of the 9×13 pan (ripping them as needed to create a single layer covering the bottom of the pan). Top tortillas with half of beef mixture. Dollop sour cream on beef mixture and spread using the back of a spoon. Place the rest of the tortillas in a single layer over the sour cream (ripping them as needed). Top with remainder of beef mixture. Sprinkle with cheese. Bake for 25 minutes.
Nutrition information per serving: 364 Calories; 116 Calories from fat; 12.9 g Total Fat (6.1 g Saturated Fat; 4.1 g Monounsaturated Fat); 71 mg Cholesterol; 431.4 mg Sodium; 34.5 g Total Carbohydrate; 6.2 g Dietary Fiber; 25.7 g Protein; 3.4 mg Iron; 734.7 mg Potassium; 0.1 mg Thiamin; 0.3 mg Riboflavin; 7.7 mg Niacin (NE); 0.3 mg Vitamin B6; 1.8 mcg Vitamin B12; 4.9 mg Zinc; 17.2 mcg Selenium; 76.9 mg Choline.
This recipe is an excellent source of Dietary Fiber, Protein, Riboflavin, Niacin (NE), Vitamin B12, Zinc, and Selenium. It is a good source of Iron, Potassium, Thiamin, Vitamin B6, and Choline.