Starting out, preheat your oven to 425°F.
In a large bowl, add cut peppers and onions, seasoning them with salt, pepper and garlic with about 1 Tbsp of olive oil. Mix until everything is combined.
Get out a large sheet pan and spread the peppers and onions flat on ½ the tray.
Next, take a bowl and add in chicken, olive oil and seasoning. Mix everything until the chicken is covered.
Spread the chicken on the other half of the sheet pan so every piece is flat to help it all cook evenly.
Place the sheet pan in the oven and bake for 30-40 minutes or until the chicken is at least 165°F and the peppers are roasted.
Lastly, let everything cool for 5 minutes before serving (can be used to make tacos, quesadillas, over rice or just placed in a meal prep container for a easy meal later).