Step 1

Coat a large nonstick skillet with cooking spray; add oil and heat over medium-high heat. Add chicken; cook and stir until no longer pink. Remove from the skillet; cover and keep warm.

Step 2

Cook onion in the same skillet about 5 minutes or until tender. Add tomatoes, tomatillos, green chile peppers, garlic, cumin, oregano, and salt. Simmer, uncovered, 10 to 12 minutes or until most of the liquid has evaporated and the tomatillos are tender; stir occasionally. Stir in the cooked chicken; heat through.

Step 3

Cut tortillas into quarters; layer over top of the chicken mixture. Sprinkle with grated cheese. Cover and let stand 1 to 2 minutes or until the cheese melts.

Step 4

To serve, top with shredded lettuce, cilantro, and Greek yogurt. If desired, garnish with jalapeño pepper slices, sliced scallion, and/or chopped fresh tomato.