Preheat the oven to 400°F. Spray a nonstick baking sheet with nonstick spray.
Spray a nonstick skillet with nonstick spray; set over medium-high heat. Add the turkey, onion, garlic, chili powder, oregano and cumin. Cook, breaking up the turkey with a wooden spoon until browned, about 6 minutes. Stir in the tomato sauce and chiles; bring to a boil. Reduce heat and simmer, uncovered, until the flavors are blended and the mixture thickens slightly, about 5 minutes. Remove from heat and stir in the cheddar.
Meanwhile, wrap the tortillas in foil and place in the oven to warm for 10 minutes.
Spoon about ½ cup of the filling into the center of each tortilla. Fold in the sides, then roll to enclose the filling. Place the chimichangas, seam-side down, on the baking sheet. Lightly spray the tops of the tortillas with nonstick spray. Bake until golden and crisp, about 20 minutes. Do not turn.
Top these chimichangas with your favorite salsa, sour cream and guacamole for extra calories, of course).