Heat oven to 375°F. Spray large cookie sheet with cooking spray. Separate dough into 8 rectangles; firmly press perforations to seal. Sprinkle about 1/8 teaspoon oregano over each rectangle. Starting with 1 short side, carefully roll up each rectangle. Cut each roll into 6 crosswise slices, making a total of 48 slices.
Form 2 trees on cookie sheet using 24 slices each. For first tree, place 1 slice for top on 1 side of cookie sheet. Arrange 2 slices below top, sides almost touching. Continue arranging rows of 3 slices, 4 slices, and continuing until last row is 6 slices across. Center 3 slices below tree for trunk.
Repeat for second tree, assembling in opposite direction on cookie sheet to fit next to first tree. Bake 14 to 18 minutes or until light golden brown. Meanwhile, with small cookie cutter or sharp knife, cut two 1 to 1 1/2-inch star shapes from bell pepper. Set aside.
Remove partially baked trees from oven. Spread 2 tablespoons of the pizza sauce evenly over each tree to within 1/2 inch of edges, leaving trunk uncovered. Sprinkle 1/4 cup chopped pepperoni evenly over sauce on each tree. Sprinkle each with 1/2 cup cheese.
Return to oven; bake 3 to 5 minutes longer or until cheese is melted. Meanwhile, heat remaining 3/4 cup pizza sauce in small saucepan until hot.
Remove trees from oven. Sprinkle each tree with 2 tablespoons tomato and 1 tablespoon onions. Place bell pepper stars on tops of trees. Cool trees on cookie sheet 2 to 3 minutes. Carefully slide trees onto serving platters, trays or cutting boards. Serve warm with warm pizza sauce for dipping.