Preheat oven to 350°F (175°C). Grease a 9x13 inch baking dish.
In a large skillet, heat oil over medium heat. Add chopped onion and bell pepper and cook until softened, about 5-7 minutes.
In a large bowl, combine cream of mushroom soup, cream of chicken soup, Rotel (undrained), chicken broth, chili powder, cumin, and garlic powder. Stir until smooth.
Spread a thin layer of sauce (about 1/2 cup) in the baking dish. Arrange 4 corn tortillas on top.
Top tortillas with half of the chicken, half of the vegetables, and 1/3 of the sauce. Sprinkle with 1/3 of the cheese.
Repeat layers: 4 tortillas, remaining chicken, remaining vegetables, and another 1/3 of the sauce. Sprinkle with 1/3 of the cheese.
Finish with the last 4 tortillas, remaining sauce, and remaining cheese.
Cover with foil and bake for 20 minutes. Remove foil and bake for another 10-15 minutes, until cheese is melted and bubbly.
Rest for 5-10 minutes before serving.