Spicy Chicken Enchiladas

1/2 cup chopped onion (1 medium)

1/4 teaspoon salt

1/4 teaspoon dried oregano leaves

1/8 teaspoon pepper

1/2 cup Old El Paso® enchilada sauce (from 10-oz can)

1 cup shredded Cheddar cheese (4 oz)

1/2 cup sour cream

2 tablespoons Old El Paso® chopped green chiles (from 4 1/2-oz can)

4 Old El Paso® flour tortillas for burritos (8 inch) (from 11 1/2-oz package)

1/2 cup chopped lettuce

1/2 cup chopped tomato (1 small)