Make the marinade: In a bowl, whisk olive oil, lemon zest and juice, garlic, oregano, thyme, salt, pepper, paprika, and red pepper flakes if using.
Marinate the chicken: Slice breasts into even cutlets or use thighs whole. Add chicken to a zip-top bag or bowl and pour in marinade.
Toss to coat. Marinate at least 30 minutes, ideally 2–4 hours. Overnight is even better.
Cook your base: While the chicken marinates, cook rice, quinoa, or couscous according to package directions.
Fluff and let it cool slightly so it doesn’t steam the veggies later.
Prep the veggies: Chop cucumber, halve cherry tomatoes, thinly slice red onion, and dice the red bell pepper if using. Toss with a pinch of salt, a drizzle of olive oil, and a squeeze of lemon. Stir in chopped parsley or dill.
Cook the chicken: Heat a large skillet or grill pan over medium-high heat.
Add a light drizzle of oil. Cook chicken 4–6 minutes per side (cutlets) or 6–8 minutes per side (thighs), until browned and cooked through. Internal temp should reach 165°F (74°C).
Rest and slice: Transfer chicken to a plate and rest 5 minutes.
Slice into strips or cubes to fit your containers.
Assemble the bowls: Divide the grain base among 4 meal prep containers. Add sliced chicken, veggie mixture, olives, and feta. Spoon tzatziki into a small sauce cup or add on the side.
Add lemon wedges if you like.
Cool before sealing: Let everything come to room temp for 10–15 minutes so condensation doesn’t make the bowls soggy.
Seal and store: Close containers and refrigerate. Keep tzatziki separated if you prefer a crisper texture.