Preheat oven to 350 degrees.
Heat oil in non-stick skillet. Saute onion and ham until onion turns translucent; remove from heat and let cool.
In a large bowl, whisk together egg, egg whites, cheese, scallions, thyme, black pepper and cooled ham mixture.
Spray mini muffin tins well with cooking spray. Divide egg mixture among 24 mini muffin tins.
Bake 20 minutes or until set.
Adapted from Cooking Light