Preheat your oven to 400°F and line a large sheet pan with parchment paper for easy cleanup.
Dice the red potatoes into small, half-inch cubes and trim the ends off the green beans.
Slice the chicken breast into even, bite-sized strips to ensure they cook at the same rate as the vegetables.
In a large bowl, toss the chicken, potatoes, and green beans with the olive oil, garlic powder, oregano, sea salt, and black pepper until well coated.
Spread the mixture in a single layer on the prepared sheet pan, ensuring nothing is overcrowded so the potatoes get crispy.
Roast in the oven for 15 minutes, then remove the pan and add the cherry tomatoes to the tray.
Return to the oven for another 8 to 10 minutes until the chicken is cooked through and the tomatoes have just begun to burst.
Remove from the oven and serve immediately, topped with fresh slices of creamy avocado.