Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Chop the zucchini and red bell pepper into half-inch pieces and spread them across one side of the baking sheet.
Place the chicken breast on the other side of the sheet and season the entire tray with half of the sea salt, black pepper, and dried oregano.
Drizzle the olive oil over the vegetables and chicken, then roast for 18 to 20 minutes until the chicken reaches an internal temperature of 165°F.
While the tray roasts, gently warm the pre-cooked lentils in a small saucepan over low heat.
Once the chicken is done, let it rest for 5 minutes before dicing it into bite-sized cubes.
In a large mixing bowl, combine the warm lentils, roasted vegetables, and diced chicken.
Add the lemon juice and the remaining salt, pepper, and oregano, then toss everything together until well combined and fragrant.