In a large mixing bowl, whisk together 1/4 cup olive oil, lemon juice, minced garlic, dried oregano, dried thyme, 1/2 tsp salt, and 1/4 tsp black pepper until well combined.

Add the chicken thighs to the marinade, tossing to ensure all pieces are thoroughly coated. Cover the bowl and refrigerate for at least 30 minutes, or up to 4 hours, to allow the flavors to meld.

Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.

While the chicken marinates, chop the red and yellow bell peppers into 1-inch pieces and cut the red onion into wedges or thick slices. Halve the cherry tomatoes and Kalamata olives if desired.

Arrange the marinated chicken thighs on the prepared baking sheet. Scatter the chopped bell peppers, red onion, cherry tomatoes, and Kalamata olives around the chicken. Drizzle the remaining 1 tablespoon of olive oil over the vegetables, and any leftover marinade from the chicken bowl.

Bake for 25-30 minutes, flipping the chicken and stirring the vegetables halfway through, until the chicken is cooked through (internal temperature reaches 165°F/74°C) and the vegetables are tender-crisp. If you prefer a bit more browning on the chicken and vegetables, you can broil for the last 2-3 minutes, watching carefully to prevent burning.

Remove the sheet pan from the oven. Garnish generously with fresh chopped parsley and crumbled feta cheese (if using). Serve immediately with a side of couscous, quinoa, or rice, or a simple green salad.