Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Dice the chicken breast, gold potato, and zucchini into uniform 1-inch cubes to ensure even cooking.
In a large mixing bowl, combine the diced chicken and vegetables with the olive oil, sea salt, black pepper, garlic powder, and dried oregano.
Toss the mixture thoroughly until every piece is evenly coated with oil and seasonings.
Spread the medley in a single layer on the prepared baking sheet, ensuring the pieces are not overcrowded.
Roast for 20 to 25 minutes, tossing halfway through, until the potatoes are tender and the chicken is cooked through to an internal temperature of 165°F.
While the medley roasts, gently warm the pre-cooked brown rice in a small saucepan or microwave.
Divide the warm rice into bowls and top with the roasted chicken and vegetable mixture.
Finish with a fresh squeeze of lemon juice over the top to brighten the flavors before serving.