Cut the chicken breasts into even pieces. In a bowl, combine olive oil, garlic powder, paprika, salt, and pepper for the marinade. Coat the chicken and marinate for 15-20 minutes.

Preheat a skillet over medium-high heat. Cook the marinated chicken pieces for 5-7 minutes on each side until golden brown and cooked through. Use a meat thermometer to check for doneness.

Prepare quinoa or brown rice according to package instructions, using vegetable broth instead of water to cook. Cook for 15-20 minutes until soft.

Whisk together Greek yogurt, lemon juice, garlic, and olive oil in a bowl until smooth for the sauce. Adjust seasoning with salt.

Assemble bowls with grains as the base, topped with sliced chicken, vegetables, and a drizzle of sauce. Add feta and herbs as desired.