Cut the chicken breast into uniform 1-inch chunks and season evenly with sea salt, black pepper, and dried oregano.
Heat the avocado oil in a large stainless steel or cast iron skillet over medium-high heat until the oil is shimmering.
Place the chicken chunks in the pan in a single layer, ensuring they are not crowded to allow for proper browning.
Sear the chicken for 3 to 4 minutes without moving them until a deep golden crust forms on the bottom.
Flip the chicken chunks, add the minced garlic to the pan, and cook for an additional 3 minutes until the chicken is cooked through.
While the chicken finishes, steam the broccoli florets in a steamer basket for 4 to 5 minutes until tender-crisp and bright green.
Turn off the heat on the skillet and drizzle the lemon juice over the chicken, scraping the bottom of the pan to release the flavorful browned bits.
Serve the seared chicken chunks alongside the steamed broccoli over a bed of warm cooked quinoa.