Marinate the chicken. In a bowl, mix olive oil, garlic, lemon zest and juice, oregano, cumin, smoked paprika, salt, and pepper. Add chicken and toss to coat. Marinate at least 20–30 minutes (or up to 24 hours in the fridge).
Make the tzatziki. Grate the cucumber, then squeeze out excess water with a clean towel.
Stir together Greek yogurt, cucumber, garlic, lemon juice, dill or mint, olive oil, salt, and pepper. Adjust lemon and salt to taste. Chill until ready to use.
Cook your base. Cook rice, quinoa, or farro according to package directions.
Fluff and let it cool slightly. If you prefer a lighter bowl, chop a hearty bed of romaine or mixed greens.
Cook the chicken. Grill over medium-high heat 5–6 minutes per side until cooked through, or pan-sear in a hot skillet with a little oil, 5–7 minutes per side. Rest for 5 minutes, then slice or chop.
Prep the veggies. Halve tomatoes, slice red onion and cucumber, and pit the olives if needed.
Crumble the feta and chop fresh parsley or dill.
Assemble the bowls. Add your grain or greens to each bowl. Top with chicken, tomatoes, cucumber, red onion, olives, and feta. Add a generous scoop of tzatziki.
Finish with freshness. Squeeze a lemon wedge over the top.
Drizzle with a little olive oil and sprinkle herbs or red pepper flakes if you like heat.