Saute olive oil with garlic, onions, and bell peppers in a cast iron skillet until semi-cooked (about 5 minutes). Set aside.
Whisk eggs, milk, and spices in a large bowl. Stir in the cooked veggies and cheese.
Line your muffin tin with silicon liners, then evenly distribute batter amongst the cups.
Bake for 30 minutes, or until internal temperature reaches 165 degrees F.
Let cool 10 minutes before serving.
Enjoy warm. Refrigerator in an airtight container for 5 days, or freeze for up to 3 months.
To ensure even cooking, chop all of the veggies approximately the same size. This will also make for easy chewing, especially for little ones!
While baking, the eggs will expand and then deflate while cooling, so be careful to not fill the cups completely otherwise they may expand beyond your cups!
If you want to make these Southwestern Egg Frittatas a full meal for a dinner or guests, then bake this in a cast iron skillet or 9x13 greased baking dish! Plus, it's a mess free clean up!
I prefer using silicon muffin liners for egg muffin recipes (if not using silicon, be sure use a little non-stick spray on the muffin tin). They make popping the frittatas out of the liner SO MUCH EASIER! You can get them off Amazon for under $10!