Cut the chicken breast into 1-inch cubes and place them in a medium bowl.
Chop the red bell pepper and red onion into 1-inch pieces, and slice the zucchini into half-moons.
In a small jar, whisk together the olive oil, lemon juice, oregano, garlic powder, salt, and pepper to create the marinade.
Pour the marinade over the chicken and vegetables, tossing well to ensure every piece is evenly coated.
Thread the chicken and vegetables onto skewers, alternating between meat and produce for even cooking.
Preheat a grill or grill pan over medium-high heat and lightly grease with a touch of oil.
Grill the skewers for 10-12 minutes, turning occasionally, until the chicken is cooked through and the vegetables are tender and slightly charred.