Make the tzatziki: Grate the cucumber on the large holes of a box grater. Squeeze out excess moisture with your hands or a clean towel. Stir together yogurt, cucumber, garlic, dill, lemon juice, olive oil, salt, and pepper.
Taste and adjust lemon or salt. Chill while you prep everything else.
Cook the base: If you haven’t already, cook your rice or quinoa according to package directions. Fluff, then stir in a squeeze of lemon, a drizzle of olive oil, and a pinch of salt for extra flavor.
Season the chicken: In a small bowl, mix oregano, cumin, paprika, thyme, red pepper flakes (if using), salt, and black pepper.
Brown the chicken: Heat olive oil in a large skillet over medium-high heat.
Add garlic and cook 30 seconds until fragrant. Add ground chicken and break it up with a spatula. Sprinkle the spice mix over the meat and cook 6–8 minutes, stirring, until browned and cooked through.
Finish the chicken: Reduce heat to medium.
Squeeze in lemon juice and stir to coat. Taste and adjust seasoning with more salt, pepper, or lemon if needed.
Prep the veggies: While the chicken cooks, chop the cucumbers, halve tomatoes, slice the onion, and pit and halve the olives. Crumble the feta and chop the herbs.
Assemble the bowls: Add a scoop of rice to each bowl.
Top with ground chicken, cucumbers, tomatoes, red onion, and olives. Add a generous spoonful of tzatziki and a sprinkle of feta. Finish with fresh herbs, a drizzle of olive oil, and a splash of red wine vinegar or lemon if you like.
Serve: Offer extra tzatziki and lemon wedges at the table.
Enjoy warm or at room temperature.