Preheat the oven to 350°F. Chop the vegetables into evenly sized pieces, about 1 inch or smaller. Heat the olive oil in a skillet over medium heat.
Add the potatoes to the hot oil and cook for about 5 minutes, until they begin to brown. Stir in the onions, cover, and cook for another 8 to 10 minutes, until the potatoes are fork-tender. Transfer the mixture to a 9 x 13 casserole dish.
Add the vegetables to the skillet and cook for about 3 minutes, until they just begin to soften. Spoon them over the potatoes in the casserole dish, then sprinkle ¾ cup of cheese evenly over the top.
Whisk the eggs with the milk and garlic powder, then pour the mixture evenly over the ingredients in the casserole dish.
Bake at 350 until done - about 40 to 45 minutes until eggs are cooked through
Video
Notes
Store leftover vegetable breakfast casserole in the refrigerator for up to four days. Reheat it in the microwave or the oven.Make Ahead Instructions:
Prep only: Chop the veggies and potatoes, store separately, and refrigerate up to 3 days. When you're ready, cook, whisk the eggs and milk, then bake.
Partly cooked: Cook the potatoes and veggies, add them to a baking dish, cover, and chill up to 3 days. Then whisk eggs, milk, and garlic, pour on, and bake.
Fully baked: Bake the whole casserole, cool, and refrigerate leftovers up to 3 days. Reheat in the oven or microwave. Don't freeze it.