1.Spray a large saucepan with nonstick cooking spray. Add onion and cook over medium-high heat for 5 minutes until lightly brown, stirring often.
2.Stir in tomatoes, peppers, garlic, oregano, and salt and cook for a few more minutes.
3.Pour mixture into a blender container, cover with a tight fitting lid, and blend until smooth.
4.Place mixture back into saucepan. Bring to a boil, and then simmer over medium heat for 5 minutes.
5.Add crisp tortillas to saucepan; cook for 2 to 3 minutes more.
6.Sprinkle with cheese then cover and let stand for a minute or so more to melt cheese.
8.*To crisp tortilla wedges, spray on both sides with nonstick cooking spray. Bake in a single layer at 425°F for 10 to 12 minutes or until lightly browned and crisp.