Chicken Fajitas with Crunchy Lime Cabbage and Avocado

Name: Chicken Fajitas with Crunchy Lime Cabbage and Avocado
Ingredients: 6 tablespoons olive oil, divided, plus additional for griddle; 2 garlic cloves, minced; 1 tablespoon chili powder; 2 pounds skinless boneless chicken breast halves, cut crosswise into 1/2-inch-thick slices; 1 large red bell pepper, cut into 3/4-inch-thick strips; 1 large red onion, halved, sliced lengthwise; 3 cups thinly sliced red cabbage; 2 tablespoons chopped fresh cilantro; 2 tablespoons fresh lime juice; 2 teaspoons finely grated lime peel; 6 to 8 fajita-size flour tortillas; 1 avocado, halved, pitted, sliced