Gather the ingredients and preheat the oven to 400°F (250°C).
Place the chicken breast and mixed vegetables straight from the freezer in a baking tray and drizzle with vegetable oil.
Season with salt and pepper, and bake in the preheated oven for 20 minutes, until the chicken is cooked through. Remove from the oven and add the crumbled feta cheese. Return to the oven for 10 more minutes, adding a bit of water if needed.
Remove from the oven and drizzle with lemon juice. Serve hot.