Preheat oven to 400°F (200°C). Wrap each beet in foil and roast for about an hour until tender. Let cool before peeling and slicing.

Rinse mixed greens under cold water and pat dry.

Cut avocados in half, remove pits, scoop out flesh, and chop into bite-sized pieces. Peel and segment the oranges.

In a large bowl or platter, layer mixed greens as the base. Top with sliced beets, orange segments, and avocado pieces.

Drizzle balsamic vinegar and olive oil over the salad; toss gently to combine without mashing the avocado.

Sprinkle crumbled feta on top before serving immediately.