Combine olive oil, lemon juice, minced garlic, and herbs in a bowl to create the marinade. Whisk until well blended and fragrant.
Place the chicken chunks in a large zip-top bag or shallow dish, then pour the marinade over the meat. Seal or cover and refrigerate for at least 30 minutes, up to 4 hours, to allow the flavors to soak in.
Preheat the grill to medium-high heat until the grates are hot and slightly smoky, about 10 minutes. Meanwhile, prepare the vegetables by slicing bell peppers and red onion into thick chunks.
Thread the marinated chicken pieces onto skewers, alternating with slices of bell peppers and onion, making sure to leave some space for even cooking.
Brush the assembled skewers with a little olive oil to prevent sticking and enhance charring, then place them on the hot grill.
Grill the skewers for about 6-8 minutes per side, turning occasionally. You’ll hear the sizzle and see the vegetables beginning to char while the chicken develops a golden crust.
Check the chicken’s internal temperature with a meat thermometer; it should reach 165°F. The vegetables should be tender with visible grill marks and slight charring.
Remove the skewers from the grill and let them rest for a couple of minutes. Brush with a little more olive oil if desired, then serve hot, showcasing the smoky, juicy chicken with charred vegetables.