Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Cut the chicken breast and the red bell pepper into uniform 1-inch cubes to ensure even cooking.
In a large bowl, toss the chicken and bell peppers with the extra virgin olive oil, sea salt, black pepper, garlic powder, and dried oregano until well coated.
Spread the chicken and pepper mixture in a single layer on the prepared baking sheet, ensuring they are not crowded.
Roast in the center of the oven for 18 to 20 minutes, or until the chicken is cooked through and the peppers are slightly charred.
While the chicken roasts, slice the mini cucumbers into thin rounds and set aside.
Gently reheat the cooked brown rice in a small saucepan or microwave until steaming.
To assemble, portion the warm brown rice into a bowl and top with the roasted chicken and peppers.
Garnish with the fresh sliced mini cucumbers and drizzle the fresh lemon juice over the entire medley for a bright finish.