Mix oil, lemon juice and zest, garlic, thyme, salt, and pepper in a small bowl.
Put chicken in a resealable bag or shallow dish.
Pour marinade over chicken to coat.
Seal or cover; refrigerate at least 30 minutes, up to 4 hours.
Heat grill to medium-high or oven to 375°F (190°C).
Remove chicken; discard marinade.
Grill 6-8 minutes per side until internal temperature reaches 165°F (74°C). Alternatively, bake on a lined sheet 25-30 minutes.
Rest a few minutes before slicing.
Serve hot with preferred sides and optional extra lemon slices and thyme.