In a large bowl, mix together Greek yogurt, lemon juice, lemon zest, dried herbs and fennel seed. Season with salt and pepper to your liking.
Place chicken thighs in yogurt mixture making sure to fully coat each piece. Cover and let marinate in the fridge for at least 1 hour but no longer than overnight.
Preheat grill to medium high. Grill chicken for approximately 15-20 minutes flipping halfway through. The chicken will be done when they reach an internal temperature of 165° F and juices run clear.
Let rest 5 minutes prior to serving.
Notes
Skinless thighs can be used for a healthier option.