Heat oven to 375F. Spray 13×9-inch (3-quart) glass baking dish with cooking spray. In medium bowl, stir Bisquick mix and water until soft dough forms. Drop half of dough by spoonfuls evenly in bottom of baking dish (dough will not completely cover bottom of dish).
Drizzle about 1 cup pizza sauce over dough. Arrange 1/2 of the pepperoni slices evenly over sauce. Top with 1 cup of the cheese. Repeat layers with remaining dough, pizza sauce, pepperoni and cheese.
Bake 20 to 25 minutes or until golden brown. Cut into squares to serve.