Heat oven to 375°F. Spray cookie sheet with cooking spray. Cook spinach in microwave as directed on box. Drain spinach in strainer; cool 5 minutes. Carefully squeeze with paper towel to drain well.
In 10-inch skillet, heat oil over medium heat. Add onion and garlic; cook 2 to 3 minutes, stirring occasionally, until crisp-tender. Remove from heat. Stir in spinach, bacon, chicken, cheese and mayonnaise.
Unroll dough on work surface. Spread spinach mixture on rectangle to within 1/2 inch of edges. Starting at long side of rectangle, roll up; seal long edge. With serrated knife, cut into 20 slices. Place cut side down on cookie sheet. Brush with egg.
Bake 10 to 15 minutes or until golden brown. Remove from cookie sheet. Serve warm.