Prepare the Ingredients: Start by preheating your oven to 400°F (200°C). While the oven heats, slice the chicken breasts into thin strips, along with the bell peppers and onion. Place them all in a large mixing bowl.
Season the Ingredients: Drizzle olive oil over the chicken and vegetables. Sprinkle with chili powder, cumin, paprika, garlic powder, onion powder, salt, and black pepper. Toss everything together until well-coated. Make sure every piece of chicken and vegetable is coated with the seasoning for maximum flavor.
Arrange on a Sheet Pan: Spread the seasoned chicken and veggies on a large sheet pan in an even layer. Avoid overcrowding, as this can lead to steaming rather than roasting.
Bake: Place the sheet pan in the preheated oven and bake for 20 minutes or until the chicken is fully cooked and the vegetables are tender. If you prefer a slightly charred finish, turn on the broiler for the last 2-3 minutes of cooking.
Serve: Once done, remove the pan from the oven and squeeze fresh lime juice over the fajitas. Serve with warm tortillas and any toppings you like, such as sour cream, shredded cheese, or avocado slices.