Soak the skewers (if wooden): Submerge in water for at least 20–30 minutes. This prevents burning on the grill.

Prep the chicken: Cut chicken into 1.25-inch cubes. Keep the pieces even for consistent cooking.

Prep the veggies: Cut bell peppers, onion, and zucchini into similar 1–1.25-inch chunks. Pat dry so they char well.

Make the garlic butter marinade: In a small saucepan over low heat, melt the butter. Add olive oil and minced garlic. Warm just until fragrant, about 30–45 seconds. Remove from heat and stir in lemon zest, lemon juice, parsley, smoked paprika, salt, pepper, and red pepper flakes (if using).

Marinate: Add chicken to a bowl and pour in about two-thirds of the garlic butter mixture. Toss to coat. Cover and refrigerate for 20–45 minutes. Reserve the remaining mixture for brushing during grilling.

Preheat the grill: Heat a gas or charcoal grill to medium-high (about 400–450°F). Lightly oil the grates to prevent sticking. For indoor cooking, preheat a grill pan over medium-high.

Skewer: Thread chicken and veggies onto skewers, alternating for color and even cooking. Don’t pack too tightly; a little space helps heat circulate.

Grill the kabobs: Place skewers on the grill. Cook for 8–12 minutes total, turning every 2–3 minutes. Brush lightly with the reserved garlic butter after each turn.

Check doneness: Chicken is done at an internal temperature of 165°F (74°C). The edges should have light char and the veggies should be crisp-tender.

Rest and garnish: Let kabobs rest for 3–5 minutes. Sprinkle with extra parsley and serve with lemon wedges.