Prepare the marinade: In a small bowl, whisk together the olive oil, lemon juice, minced garlic, thyme, and oregano. Transfer the marinade to a resealable bag.
Cut 3-4 shallow slits on top of each chicken breast. Place the chicken in the bag. Use clean hands to coat the chicken well. Seal the bag, removing as much air as possible. Marinate the chicken at room temperature for 30 minutes.
Spray the lemon slices on both sides with olive oil. Set aside.
Remove the chicken from the marinade and discard the bag with the marinade. Season the chicken pieces with salt and pepper on both sides.
Heat a lightly greased grill pan over medium heat. Place the chicken breasts on the hot grill. Grill them until browned on the bottom, about 7 minutes.
Turn the chicken pieces over and add the lemon slices to the pan. Continue cooking the chicken until it's fully cooked, about 7 more minutes. Flip the lemon slices midway through cooking.
Remove the chicken from the grill onto a cutting board. Cover it with foil and allow it to rest for 10 minutes. Slice it, top it with chopped parsley, and serve it with the grilled lemon slices.
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Notes
It's best to use an instant-read thermometer to ensure the chicken is fully cooked and reaches an internal temperature of 165°F. I wrote this recipe for 8 oz chicken breasts. If yours are much bigger, they will need more time on the grill.
It's important to let the chicken rest for a minimum of 5 minutes before slicing it. This helps ensure that the juices will settle and redistribute and helps keep the chicken nice and juicy.