In a small bowl, beat together eggs, milk and onions until blended. In a 7 or 8-inch skillet over medium heat, heat butter until just hot enough to sizzle a drop of water. Pour in egg mixture. As mixture begins to set, gently draw an inverted pancake turner completely across bottom and sides of pan, forming large, soft curds. Continue until eggs are thickened and no visible liquid egg remains. Spoon 1/4 of the eggs into each pita half. If you like, add chopped tomato and green pepper, a sprinkling of shredded cheese or a dollop of taco sauce, or all of them!