Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Wash and dice the Yukon Gold potatoes into 1/2-inch cubes, then place them on one side of the prepared baking sheet.
Toss the potatoes with 0.5 tsp of olive oil, half of the dried oregano, half of the garlic powder, and a pinch of the salt and pepper.
Place the baking sheet in the oven and roast the potatoes for 15 minutes.
While the potatoes are roasting, pat the chicken breast dry and rub it with 0.5 tsp of olive oil and the remaining oregano and garlic powder.
Carefully remove the baking sheet from the oven, slide the potatoes to one side, and add the chicken breast and trimmed green beans to the empty space.
Drizzle the green beans with the final 0.5 tsp of olive oil and the remaining salt and pepper.
Return the pan to the oven and roast for an additional 15 to 20 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden brown.
Remove from the oven, drizzle the fresh lemon juice over the entire tray, and garnish with freshly chopped parsley before serving.