Preheat the oven to 425 degrees. Line a large baking sheet with foil.
In a small bowl, stir together the cumin, chili powder, salt & pepper.
Add the chicken, bell peppers and red onion to the prepared baking sheet.
Drizzle oil and sprinkle the seasoning over the sheet pan and then toss to combine.
Bake for 20 - 25 minutes, flipping halfway. The vegetables should be tender and the chicken cooked through.
Remove from the oven and squeeze the juice of 1 lime over the sheet pan.
Serve immediately. Serve as fajitas (with tortillas), or in Fajita Chicken Burrito Bowls.