1. Place each filleted chicken breast on a cutting board, cover with plastic wrap, and pound until even about 1/2-inch thick.
2. In a bowl, zest one lemon and juice two lemons. Add the olive oil, salt and pepper. Whisk to combine. Place the chicken in a zip-top bag with the marinade and refrigerate for 1-4 hours.
3. Preheat grill to medium-high heat.
4. Remove chicken from the marinade and allow excess marinade to drip off (or lightly wipe off with paper towel). Drizzle some olive oil on a towel and wipe down the grill grates.
5. Cut the remaining two lemons in half.
6. Place the chicken and lemons (cut side down) on direct heat. After two minutes, rotate the chicken 45 degrees. After two more minutes flip and repeat. Remove (chicken should be at 165°F internal temp) and place one piece of chicken on each plate.