In a large skillet over medium-high heat, cook ground beef, green pepper, squash, and onion until ground beef is no longer pink.
Reduce heat to low and add beans, salsa, 1/2 can of the enchilada sauce, and taco seasoning and cook until heated through. Let simmer for 5 minutes so that the flavors can meld together.
Pour 1/3 of the meat mixture in the bottom of the slow cooker sprayed with nonstick cooking spray, sprinkle 1/2 cup of the cheese over the meat and top with two tortillas (they will overlap a little in the middle). Repeat layers two more times.
Pour the remaining enchilada sauce over the top of the tortillas (spread with a spatula if you need to) and top with the remaining 1/2 cup of cheese.
Cover with lid and cook on low for 3-4 hours (just until it's heated through)
Scoop servings onto plates and top with your favorite toppings.
Notes
To make these in the oven:What I would do for an oven is just make this in a 9x13" pan. Follow steps #2 and #3, then spray a 9x13" pan with non-stick cooking spray. Layer the meat mixture and tortillas in the pan, top with enchilada sauce and cheese, then bake at 350 degrees for about 30 minutes. It will be more like a casserole, but still just as delicious!