Preheat the oven to 350 degrees F (175 degrees C).

Mix soup and sour cream in a small bowl; set aside.

Melt margarine in a medium saucepan over medium-high heat. Add onion and chili powder, and sauté until tender. Stir in chicken, chile peppers, and 2 tablespoons of the soup mixture. Cook and stir until heated through.

Spread 1/2 cup of the soup mixture in a 9x13-inch baking dish. Spoon about 1/4 cup of the chicken mixture down the center of each tortilla. Roll up tortillas and place, seam-sides-down, in the baking dish. Spoon remaining soup mixture on top, and sprinkle with cheese.

Bake in the preheated oven until bubbly and lightly browned, about 25 minutes.