In a medium bowl, whisk together 2 tablespoons of olive oil, minced garlic, lemon juice, lemon zest, oregano, salt, and pepper.
Add the cubed chicken to the marinade and toss to coat thoroughly; marinate for at least 10 minutes.
Preheat a large skillet over medium-high heat with the remaining 1 tablespoon of olive oil.
Add the chicken to the skillet in a single layer and cook for 8-10 minutes, turning occasionally until browned and the internal temperature reaches 165°F (74°C).
Steam or roast broccoli until tender-crisp and bright green.
Divide the cooked brown rice evenly among four meal prep containers.
Top each container with a portion of the lemon garlic chicken and the prepared broccoli.
Allow meals to cool slightly before sealing and refrigerating for up to 4 days.