Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Chop the broccoli into bite-sized florets, slice the bell peppers into strips, and wedge the red onion.
In a large bowl, toss the vegetables with 0.5 tablespoon of avocado oil, half of the sea salt, black pepper, garlic powder, and dried oregano until evenly coated.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 18-22 minutes until tender and slightly caramelized.
While the vegetables roast, pat the chicken breast dry with paper towels and season both sides with the remaining salt, pepper, garlic powder, and oregano.
Heat the remaining 0.5 tablespoon of avocado oil in a medium stainless steel or cast-iron skillet over medium-high heat.
Place the chicken in the hot skillet and sear for 5-7 minutes per side, or until the internal temperature reaches 165°F and the exterior is golden brown.
Remove the chicken from the pan and let it rest for 5 minutes before slicing to keep it juicy.
Serve the sliced pan-seared chicken alongside the warm roasted vegetables.