01 -  Set oven temperature to 425°F (220°C) to prepare for roasting. 
 02 -  In a large mixing bowl, toss chicken thighs, sliced bell peppers, and sliced red onion with olive oil and Cajun seasoning until evenly coated. 
 03 -  Spread the coated chicken and vegetables in a single layer on a baking sheet. 
 04 -  Transfer the baking sheet to the oven and roast for 25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and vegetables are tender.