Preheat your oven to 400°F (200°C).
In a large bowl, combine olive oil, lemon juice, garlic, oregano, salt, and pepper.
Add chicken thighs to the bowl and coat them well with the marinade.
Arrange the chicken in a baking dish, skin side up.
Scatter the cherry tomatoes, zucchini, bell pepper, and onion around the chicken.
Drizzle any remaining marinade over the vegetables.
Roast in the preheated oven for 35-40 minutes, or until the chicken is golden brown.
Use a meat thermometer to ensure chicken reaches 165°F (75°C) internally.
Let the dish rest for 5 minutes before serving.
Garnish with fresh herbs if desired and serve warm.