Grease a nonstick muffin tin with olive oil and evenly divide the peppers and scallions among the muffin cups.
In a large bowl, whisk the eggs. Add the garlic, salt, and several grinds of pepper, then sprinkle the flour and baking powder on top. Whisk well to combine. It’s ok if a few clumps of flour remain in the mixture.
Divide the egg mixture evenly into the muffin cups (you’ll use about a scant ¼ cup in each one). Sprinkle the feta on top.
Bake for 22 to 24 minutes, or until the eggs are set. Let cool before removing from the pan.