Preheat your oven to 400°F (200°C).
Trim and halve the Brussels sprouts, then toss them on a parchment-lined baking sheet with 0.5 tbsp of olive oil and a pinch of the salt and pepper.
Roast the sprouts for 20-25 minutes, tossing halfway through, until they are tender and the outer leaves are crispy and golden.
While the sprouts roast, season the chicken breast on both sides with garlic powder, dried oregano, and the remaining salt and pepper.
Heat the remaining 0.5 tbsp of olive oil in a medium skillet over medium-high heat.
Add the chicken to the skillet and sear for 6-8 minutes per side until the exterior is golden brown and the internal temperature reaches 165°F.
Remove the skillet from the heat, then add the lemon juice and lemon zest, swirling the pan to create a light sauce to coat the chicken.
Serve the lemon-herb chicken immediately alongside the crispy roasted Brussels sprouts.