Preheat your oven to 375°F (190°C) and generously grease your baking dish with a little olive oil.
Dice the roasted squash into small, bite-sized pieces and set aside. If you're roasting fresh squash, toss it with a splash of olive oil, salt, and pepper, then roast until golden and tender, about 20 minutes.
Peel and dice the autumn apple into small cubes, ensuring they are evenly sized for a balanced bite.
In a large mixing bowl, whisk the eggs until the whites and yolks are fully combined and slightly frothy, filling the bowl with a gentle sound of whisking.
Fold in the diced roasted squash, apple pieces, shredded cheese, chopped herbs, and a pinch of salt and pepper into the eggs. Mix gently until everything is evenly distributed, creating a colorful, cohesive mixture.
Pour the egg mixture into the prepared baking dish, spreading it out evenly with a spatula. The mixture should fill the dish about three-quarters full.
Place the baking dish in the oven and bake for about 30-35 minutes, or until the top is puffed and golden brown with a slight jiggle in the center when gently shaken.
Remove the frittata from the oven, let it rest for 5 minutes, then slice into wedges. The edges should be crisp, and the center tender and fluffy.
Serve warm, garnished with extra fresh herbs if desired, and enjoy the comforting flavors of fall in every bite.
