Season chicken with chili powder. Heat 1 tablespoon oil in 12-inch nonstick skillet over medium-high heat and cook chicken, turning once, until chicken is thoroughly cooked, about 6 minutes. Remove chicken from skillet and cool slightly; slice.
Heat remaining 1 tablespoon oil in same skillet and cook red peppers and onion, stirring occasionally, until vegetables are tender, about 8 minutes. Reduce heat to low. Stir in lime juice and Knorr® Homestyle Stock - Chicken and simmer until Stock is melted. Return chicken to skillet; toss to coat.
Serve in warmed tortillas and garnish, if desired, with your favorite fajita toppings such as shredded cheddar cheese, sour cream and/or chopped cilantro.