Preheat the oven to 375 degrees and line a sheet pan with parchment paper. Set aside
Whisk the lemon zest, juice, Greek yogurt, oregano, garlic, crushed red pepper, olive oil, salt and pepper in a small bowl until smooth.
Place the sliced chicken in the bag and pour in the marinade. Seal the bag and marinate the chicken while you prepare the rest of the meal (10-15 minutes).
While the chicken is marinating, slice the peppers and onions and set aside. Skip ahead to make the sauce.
After 10-15 minutes, remove the chicken from the bag. Season with ¾ tsp more salt and a few very generous grinds of black pepper.
Spread the chicken onto the prepared sheet pan in the middle, and surround it with the onions and peppers.
Drizzle the chicken and onions and peppers with 2 tbsp olive oil
Bake in the oven for 15 minutes, until the chicken is fully cooked. Then turn your oven to broil, and broil for 2-3 minutes so the edges begin to caramelize.