Heat oven to 375°F. Spray large cookie sheet with cooking spray. In 10-inch skillet, cook bacon until crisp; drain on paper towels. Crumble bacon; set aside. Reserve 1 tablespoon bacon drippings in skillet. Cook mushrooms in bacon drippings over medium heat 4 to 5 minutes, stirring frequently, until lightly browned.
If using crescent rolls: Unroll dough; separate into 4 rectangles. Press each into 8x4-inch rectangle, firmly pressing perforations to seal. If using dough sheet: Unroll dough; cut into 4 rectangles. Press each into 8x4-inch rectangle.
Cut each in half crosswise, making 8 squares; place 1/2 inch apart on cookie sheet.
Spread 2 teaspoons cream cheese and about 1/2 tablespoon pesto on each square. Top evenly with cooked mushrooms and 1/2 cup of the mozzarella cheese. Arrange tomato slices over cheese. Sprinkle with onions, crumbled bacon and remaining 1/2 cup cheese.
Bake 13 to 15 minutes or until crust is golden brown. Immediately remove from cookie sheet. Serve warm.