Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
In a small bowl, whisk together the vegetable oil, chili powder, oregano, garlic powder, onion powder, cumin, salt, black pepper, and cayenne pepper to create the fajita seasoning.
Place the chicken pieces, sliced bell peppers, and onion in a large bowl. Pour the seasoning mix over the chicken and vegetables, and toss until everything is well coated.
Spread the chicken and vegetables in an even layer on the prepared sheet pan.
Bake in the preheated oven for 15 minutes, or until the chicken is cooked through and the vegetables are tender and slightly charred.
Remove from the oven, sprinkle with chopped cilantro, and drizzle with lime juice. Toss to combine.
Serve your sheet pan chicken fajitas with warm tortillas, sour cream, and your favorite toppings.