Heat 1 tablespoon oil in a large skillet over medium-high heat; add chicken breasts.

Cook 6 to 7 minutes on each side or until done.

Remove from pan; cool and shred chicken.

Heat remaining 1 tablespoon oil in skillet over medium-high heat.

Add onion and garlic; cook 4 minutes or until tender.

Add tomatoes and red pepper; cook for 15 minutes or until most of liquid evaporates.

Remove from heat, and stir in shredded chicken and green chiles.

Melt butter in a heavy saucepan over low heat.

Add flour and fajita seasoning; whisk until smooth.

Cook 1 minute, whisking constantly.

Gradually add half-and-half; cook over medium heat 4 minutes or until thick and bubbly, whisking constantly.

Spread one-fourth white sauce in a lightly greased 13- x 9-inch baking dish.

Arrange 6 tortilla halves over sauce.

Top with half of chicken mixture and ⅔ cup cheese.

Repeat layers once, ending with cheese.

Spoon one-fourth sauce over the cheese, and top with remaining tortilla halves.

Spoon remaining sauce over tortillas.

Reserve remaining ⅔ cup cheese.

Bake, uncovered, at 350° for 40 minutes or until thoroughly heated.

Sprinkle with reserved ⅔ cup cheese, and bake 5 more minutes.

Garnish, if desired.