Begin zesting and juicing the two lemons, mince the garlic, and measure the oregano, thyme, salt, and pepper.

In a mixing bowl, combine olive oil, lemon juice, zest, garlic, oregano, thyme, salt, pepper, and mustard if using. Whisk until emulsified.

Place chicken in a bag or dish, pour marinade over it, ensure it's coated, seal, and refrigerate from 1 to 24 hours.

Remove chicken to room temperature for 20 minutes. Preheat grill to medium-high or oven to 400°F. Cook chicken until internal temperature reaches 165°F.

Let the chicken rest for 5 minutes, garnish, and serve with sides like Greek salad or warm pita.