In heavy bottom pot or dutch oven, heat olive oil over medium high heat. Add the onions and saute, stirring occasionally, until slightly brown and tender, about 5 minutes. Add garlic, oregano, and cumin and saute for another minute. Add flour and stir well. Cook flour with onion and garlic until fragrant, stirring frequently, about 2 minutes.
Add green chile, tomatoes, and chicken stock. Stir well to combine and scrape bottom of pan to ensure flavors are fully mixed. Bring to a boil, then reduce heat to low and simmer for 20 minutes.
Remove from heat and blend until smooth in blender. Add salt and pepper to taste.
Serve on enchiladas or breakfast burritos. Makes 8 cups.