Generously spray 12 muffin cups with cooking spray.
Heat butter in large nonstick skillet over medium heat until hot. Add broccoli, red pepper and onion, cook 3 to 4 minutes, stirring occasionally. Remove to medium bowl. Add bread and cheese; toss to mix.
Beat eggs, half-and-half, salt and pepper in small bowl until blended. Pour over bread mixture; toss gently to coat. Place about 1/2 cup bread mixture into each muffin cup. Cover and refrigerate 1 hour or overnight.
Heat oven to 350°F. Bake for 20 to 25 minutes or until puffed, golden and knife inserted near center comes out clean. Loosen stratas from sides of pans with thin knife.
Make ahead and keep refrigerated for quick weekday morning breakfasts. Reheat in the microwave on HIGH, 2 mini stratas take about 45 seconds.