In a cast iron skillet over medium-high heat, heat olive oil. Add butter, and melt in hot oil. Add green apple wedges and red apple wedges; cook, turning as necessary, to brown on both sides. Remove apples and set aside.
Add yellow onion wedges and red onion wedges; cook for about 3-5 minutes, until brown and tender, turning as necessary. Remove sautéed onions and set aside.
Add green onions and celery, and cook for about 3-5 minutes, until brown and tender. Reduce heat to medium. Add reserved apples and onions to skillet, and season with salt and pepper. Cook until combined and thoroughly warmed.