1. 1. Preheat your oven to 400 F (200 C). Line a large baking sheet with parchment paper for easy cleanup.

2. 2. Pat the boneless, skinless chicken thighs dry with paper towels. Cut them into 1.5 to 2-inch pieces. Place the chicken pieces in a large bowl.

3. 3. Cut the zucchini into 1/2-inch thick half-moons, slice the bell peppers into 1-inch strips, and cut the red onion into 1/2-inch wedges. Add all the chopped vegetables to the bowl with the chicken.

4. 4. Drizzle the olive oil over the chicken and vegetables in the bowl. Sprinkle with Italian seasoning, garlic powder, onion powder, salt, and black pepper. Toss everything together thoroughly with your hands or a large spoon until the chicken and vegetables are evenly coated in the oil and seasonings.

5. 5. Spread the seasoned chicken and vegetables in a single layer on the prepared baking sheet. Ensure there’s enough space between the pieces so they can roast rather than steam. If your baking sheet is too crowded, use two sheets.

6. 6. Place the baking sheet in the preheated oven and roast for 20-25 minutes. About halfway through (around 12-15 minutes), gently toss the chicken and vegetables to ensure even cooking and browning. The chicken should be cooked through with no pink remaining (internal temperature of 165 F or 74 C), and the vegetables should be tender-crisp and slightly caramelized at the edges.

7. 7. Once cooked, remove the sheet pan from the oven. Garnish with fresh chopped parsley, if desired, and serve hot.