Marinate the chicken. In a bowl, whisk olive oil, lemon zest and juice, garlic, oregano, cumin, salt, and pepper.
Add the chicken and toss to coat. Let it sit for at least 20 minutes, or up to 8 hours in the fridge.
Make the tzatziki. Grate the cucumber and squeeze out excess water with a clean towel. In a bowl, mix yogurt, cucumber, lemon juice, garlic, dill, olive oil, salt, and pepper.
Taste and adjust lemon or salt. Chill until ready to serve.
Cook your base. Prepare rice, quinoa, or cauliflower rice according to package directions. Fluff with a fork and season with a pinch of salt and a drizzle of olive oil.
Cook the chicken. Heat a large skillet or grill pan over medium-high.
Lightly oil the pan. Cook chicken 5–7 minutes per side, until browned and cooked through (165°F/74°C). Rest 5 minutes, then slice.
Toss the salad elements. In a small bowl, combine tomatoes, cucumber, onions, olives, olive oil, red wine vinegar, oregano, and a pinch of salt and pepper.
Assemble the bowls. Divide the base among 4 containers.
Add sliced chicken and the chopped salad. Sprinkle with feta. Add a small container or dollop of tzatziki to each bowl.
Garnish and store. Top with fresh herbs and a lemon wedge if using.
Seal and refrigerate.