Pat the chicken breast dry with paper towels and cut into 1-inch bite-sized pieces.
Season the chicken pieces evenly with the sea salt, black pepper, and dried oregano.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Add the chicken to the skillet in a single layer and sear until golden brown on all sides, about 5-6 minutes.
Remove the chicken from the pan and set aside on a clean plate.
In the same skillet, add the sliced bell peppers, diced zucchini, and sliced red onion.
Sauté the vegetables for 4-5 minutes until they are tender-crisp and slightly charred.
Stir in the minced garlic and cook for 1 minute until fragrant.
Return the chicken and any accumulated juices to the skillet, tossing everything together to combine.
Garnish with fresh chopped parsley and serve immediately.