Cut the chicken breast into 1-inch cubes and chop the red bell pepper, zucchini, and red onion into similar-sized pieces.
In a medium bowl, whisk together the avocado oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper to create the marinade.
Add the chicken and vegetables to the bowl and toss thoroughly until every piece is evenly coated in the herb mixture.
Thread the marinated chicken and vegetables onto wooden or metal skewers, alternating between the protein and the different vegetables.
Preheat a grill or a large cast-iron skillet over medium-high heat.
Cook the skewers for 10-12 minutes, turning every few minutes, until the chicken is cooked through and the vegetables are tender with a slight char.