Brown the ground beef in a skillet over medium-high heat. Drain off any excess grease.
Stir in the taco seasoning, refried beans, diced tomatoes and green chilies, and salsa. Cook for 5 minutes, stirring occasionally, until heated through.
Spread half of the tortilla wedges in the bottom of a 9×13 inch baking dish.
Spoon half of the beef mixture over the tortillas.
Sprinkle with half of the cheddar and Monterey Jack cheeses.
Repeat the layers with the remaining tortillas, beef mixture, and cheeses.
Bake for 20-25 minutes, or until the cheese is melted and bubbly.
Let stand for 5 minutes before serving. Serve with your favorite toppings.
Notes
For a make-ahead option, assemble the casserole, cover tightly, and refrigerate for up to 2 days. Bake as directed, adding an extra 5-10 minutes to the baking time.
To freeze, assemble the casserole and cover tightly with plastic wrap and then foil. Freeze for up to 3 months. Thaw overnight in the refrigerator and bake as directed.
You can also adapt this recipe for a slow cooker. Brown the beef and mix with the other ingredients (except tortillas and cheese). Cook on low for 4-6 hours or high for 2-3 hours. Layer tortillas and cheese in a serving dish and top with the slow cooker mixture.