Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Place the sourdough bread slice in a food processor and pulse until it transforms into fine, airy crumbs.
In a shallow bowl, whisk the half egg until smooth; in a separate shallow dish, combine the sourdough crumbs with half of the salt, pepper, garlic powder, and oregano.
Season the chicken breast with the remaining spices, then dip it into the egg wash, followed by the sourdough mixture, pressing firmly to ensure an even coating.
Place the crusted chicken on one side of the prepared baking sheet.
On the other side of the sheet, toss the broccoli florets and sliced bell peppers with the olive oil and a pinch of salt.
Bake for 20 to 25 minutes, or until the chicken is cooked through and the crust is beautifully golden and crispy.
Let the chicken rest for 3 minutes before serving alongside the roasted vegetables.