Step 1

Position one rack in the middle of the oven and another in the lower third, and preheat to 400 degrees.

Step 2

In a large bowl, toss together the chicken, peppers, onion, garlic, vinaigrette or oil, chili powder and salt until evenly coated. Spread on a large sheet pan and roast on the middle rack for 25 to 30 minutes, or until vegetables are tender and chicken is cooked through, stirring halfway through cooking.

Step 3

During the last 5 minutes of roasting, wrap the tortillas in foil and place in the oven on the lower rack until warmed through. (Alternatively, wrap the tortillas in clean, damp tea towels and microwave on HIGH for 1 minute.)

Step 4

Divide the fajita mixture among warm tortillas and serve warm, with sour cream on the side.