In a skillet over medium-high heat, heat 1 Tbsp oil. Add the chilies and garlic; saute until garlic is soft. Break up tomatoes and add to chilies along with onions, 1 tsp salt, oregano and 1/2 cup reserved tomato liquid. Simmer uncovered until thick, about 30 minutes. (You can add more reserved tomato liquid if sauce gets too thick too quickly.) Remove tomato sauce from heat and set aside. Heat 1/3 cup oil in a skillet over medium-high heat until hot. Dip tortillas in hot oil for a few seconds, or just until they become limp. Drain well on paper towels. Fill tortillas with chicken mixture. Roll up and arrange side by side, seam down, in a 9x13x2-inch baking dish. Pour tomato sauce over enchiladas and bake at 350 degrees until heated through, about 20 minutes. Can freeze cooked enchiladas and heat through in oven before serving.
Makes 6 servings.