In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until softened.
Add the minced garlic and cook for an additional 1 minute until fragrant.
Increase the heat to medium-high and add the ground chicken. Cook, breaking it apart with a spatula, until browned and cooked through, about 5-7 minutes.
Stir in the oregano, thyme, red pepper flakes (if using), salt, and pepper. Mix well to combine.
Add the cherry tomatoes and Kalamata olives to the skillet. Cook for another 3-4 minutes until the tomatoes soften.
Remove the skillet from heat and sprinkle the crumbled feta cheese on top.
Garnish with chopped fresh parsley before serving.