1/4 cup fresh lemon juice
1/4 cup finely chopped fresh oregano
2 tablespoons minced garlic
1 1/2 tablespoons kosher salt
2 teaspoons black pepper
1/3 cup olive oil
8 chicken breasts
2 lemons, cut crosswise into 1/3-inch-thick slices (optional)
Whisk together lemon juice, oregano, garlic, 1 tablespoon salt, and 1 1/2 teaspoons pepper in a large bowl and add oil in a slow stream, whisking.
Season chicken with 1/2 tablespoon salt and 1/2 teaspoon pepper.
Pour marinade over chicken, turning once to cover breasts. Refrigerate for up to one hour.
Cook chicken breasts over moderate heat, turning once, until just cooked through (the meat next to the tender, when opened slightly, will be moist but no longer pink), about 30 minutes total.
Grill lemon slices on rack over flames, uncovered, until grill marks appear, about 3 minutes on each side, and transfer to platter with chicken.
Notes: I usually throw everything in my food processor to save chopping time. I also double the marinade and reserve a little to serve as a sauce over the chicken before serving.