In a mixing bowl, combine diced chicken breast with olive oil, lemon juice, minced garlic, and seasonings. Marinate for at least 30 minutes in the refrigerator.

Grate cucumber, squeeze out excess moisture, and mix with Greek yogurt, more minced garlic, lemon juice, and chopped dill to prepare tzatziki.

Cook marinated chicken in a grill pan or skillet over medium-high heat for 6-8 minutes per side until cooked through.

Prepare quinoa or couscous according to package instructions, usually simmering for 12-15 minutes.

Assemble bowls with the grain base, slices of grilled chicken, tzatziki, and fresh vegetables on top.

Serve immediately while fresh and warm, adding extra tzatziki or herbs as desired.