In a small bowl, combine the olive oil, lemon juice, lemon zest, minced garlic, fresh thyme, salt, and pepper. Mix well.
Place the chicken breasts in a large resealable plastic bag or a shallow dish.
Pour the lemon thyme marinade over the chicken, ensuring each piece is well-coated.
Seal the bag or cover the dish and refrigerate for at least 30 minutes, or up to 4 hours for maximum flavor.
Preheat your grill to medium-high heat, or preheat your oven to 375°F (190°C) if you prefer to bake.
Remove the chicken from the marinade and discard the marinade.
Grill the chicken for 6-8 minutes per side, or until the chicken reaches an internal temperature of 165°F (74°C). If baking, place the chicken on a lined baking sheet and bake for 25-30 minutes.
Let the chicken rest for a few minutes before slicing and serving.
Serve hot, garnished with extra lemon slices and fresh thyme if desired. Enjoy with your favorite sides like a fresh salad or steamed veggies!