Marinate the Chicken: In a large bowl, whisk together all the marinade ingredients (minced garlic, olive oil, red wine vinegar, oregano, thyme, salt, pepper, and lemon juice). Add the cubed chicken and toss to coat. Cover the bowl and refrigerate for at least 30 minutes, or up to 2 hours.
Prepare the Sheet Pan: While the chicken is marinating, preheat your oven to 425°F (220°C). Line a large, rimmed baking sheet with parchment paper for easy cleanup.
Arrange and Season: Take the chicken out of the marinade bowl. Add the chopped red onion, bell peppers, and cherry tomatoes to the same bowl with any remaining marinade. Toss everything together until the vegetables are lightly coated.
Roast: Spread the chicken and vegetables in a single, even layer on the prepared baking sheet. Make sure not to overcrowd the pan, as this will steam the food instead of roasting it.
Bake: Bake for 20 to 25 minutes, or until the chicken is cooked through and the vegetables are tender and slightly caramelized. You may want to toss the ingredients halfway through the cooking time to ensure even browning.
Serve: Remove the sheet pan from the oven. Serve the chicken and vegetables immediately. This dish is excellent served with warm pita bread or rice, and a generous dollop of tzatziki sauce. Garnish with fresh herbs, crumbled feta, or olives as desired.