Roast the Vegetables: Place the mushrooms, bell pepper, and broccoli on an 11 x 17-inch rimmed baking sheet. Drizzle with olive oil and season with half of the salt and pepper. Toss to coat evenly, then spread into a single layer. Roast for 10–12 minutes, or until slightly tender.
Prepare the Egg Mixture: In a large bowl, whisk together the eggs, half and half, Italian seasoning, and the remaining salt and pepper until well combined and fluffy. Stir in the shredded cheddar cheese and scallions.
Bake the Frittata: Remove the baking sheet from the oven and pour the egg mixture evenly over the roasted vegetables. Return to the oven and bake for 13–17 minutes, or until the eggs are set and lightly browned around the edges.
Rest and Serve: Let the frittata rest for 5 minutes before slicing. Garnish with fresh chopped herbs, if desired. Serve warm.
Notes
Make-Ahead Tips: The egg mixture can be whisked together the night before and stored in the refrigerator for easy assembly in the morning.Storage: Store leftovers in an airtight container in the refrigerator for up to 3 days.Freezing: Slice the frittata into portions and freeze in an airtight container for up to 2 months. Reheat from frozen in the microwave or oven.Reheating: Warm individual slices in the microwave for 30–45 seconds or in a toaster oven at 350°F for 5–7 minutes.Customization Ideas: Swap out vegetables for your favorites, such as spinach, asparagus, or zucchini. Try different cheeses like feta, mozzarella, or goat cheese for a unique twist.