Dice the chicken and veggies - Cut the chicken breasts, red onion, red bell pepper, and zucchini into bite-sized chunks, about 1-2 inches in size. Keep each ingredient separate.
Preheat the grill or grill pan - Preheat your grill or grill pan on medium-high heat. Meanwhile, soak bamboo skewers in water for at least an hour if using.
Season the chicken and veggies with oil, salt, and pepper - In a large mixing bowl, add the chicken, veggies, olive oil, salt, and pepper. Toss to coat the ingredients evenly.
Skewer the chicken and veggies - Thread the chicken and veggies onto the skewers in an alternating pattern until all the ingredients are used up. Leave a little bit of space between each ingredient to ensure even cooking.
Brush the skewers with BBQ sauce and grill - Once the grill is hot, brush the skewers on both sides with BBQ sauce. Place the skewers on the grill and grill for about 10-12 minutes, turning occasionally, until the chicken is cooked through and the veggies are tender.
Serve and enjoy! - Remove the skewers from the grill and serve immediately. Drizzle with additional BBQ sauce if desired. Enjoy these easy grilled BBQ chicken skewers with your favorite sides and drinks!