Make the marinade. In a bowl, whisk olive oil, lemon juice and zest, garlic, oregano, cumin, salt, pepper, and red pepper flakes.
It should smell bright and garlicky.
Prep the chicken. Pat chicken dry, then add to the marinade and toss to coat. Cover and refrigerate for at least 30 minutes; 2–4 hours is even better for deeper flavor.
Cook your base. While the chicken marinates, cook rice, quinoa, or your chosen grain according to package directions. Fluff and keep warm.
For a low-carb option, sauté cauliflower rice with a little olive oil and salt.
Make tzatziki. Grate cucumber, then squeeze out as much liquid as possible with a clean towel or paper towels. Stir together Greek yogurt, cucumber, olive oil, lemon juice, garlic, dill, salt, and pepper. Adjust lemon and salt to taste.
Chill until serving.
Prep the veggies. Halve tomatoes, dice cucumber, slice red onion, and chop greens. Pit and slice olives if needed. Keep everything in separate bowls for easy assembly.
Cook the chicken. Heat a large skillet or grill pan over medium-high.
Add a drizzle of oil. Cook chicken 4–6 minutes per side, depending on thickness, until the outside is golden and the center reaches 165°F (74°C). Rest 5 minutes, then slice.
Assemble bowls. Add a scoop of grains to each bowl.
Top with chicken, tomatoes, cucumbers, onion, olives, and greens. Add a generous dollop of tzatziki, sprinkle with feta, and finish with fresh herbs and a squeeze of lemon.
Taste and adjust. Add a pinch of salt, extra tzatziki, or more lemon if needed. The bowl should taste bright, savory, and balanced.