Marinate the chicken thighs with olive oil, minced garlic, lemon zest, oregano, red pepper flakes, salt, and pepper.
Let this mixture sit for at least 30 minutes to enhance the flavors.
Preheat your grill to medium-high heat.
Make sure the grill grates are clean and lightly oiled to prevent sticking.
While the grill heats up, prepare the honey mustard glaze.
Combine the honey and Dijon mustard in a bowl and mix well.
Set aside for later.
Place the marinated chicken thighs on the grill.
Grill them for about 6-7 minutes on each side or until they reach an internal temperature of 165°F (74°C).
During the last few minutes of grilling, brush the chicken thighs generously with the honey mustard glaze.
Let the glaze caramelize slightly before removing the chicken from the grill.