Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup. Pat the chicken breasts dry with paper towels—this ensures proper browning and moisture retention during roasting.
In a small bowl, whisk together olive oil, minced garlic, lemon juice, dried oregano, salt, and black pepper. This marinade creates the flavor foundation that transforms ordinary chicken into Mediterranean perfection.
Place chicken breasts on the prepared sheet pan and brush generously with the herb mixture on both sides. Arrange cherry tomatoes, bell peppers, red onion, and halved baby potatoes around the chicken, drizzling vegetables with remaining marinade.
Scatter kalamata olives throughout the loaded sheet pan greek chicken and roast at 400°F for 20-25 minutes until the chicken reaches an internal temperature of 165°F. The potatoes should be tender and lightly golden when finished.
Remove from the oven and top with crumbled feta cheese and fresh parsley while everything is still warm. Let it rest for 2-3 minutes before serving to allow juices to redistribute throughout the sheet pan dinner.