Cut Ciabatta in half horizontally (like to make a big sandwich), then cut across into thirds so you have 6 pieces. Pull off some of the soft inner bread in spots where pieces are particularly thick. Set aside.
Slice chicken into thin bite size strips and slice mushrooms.
Heat oil in skillet over med to med-high heat. Add chicken, mushrooms and oregano, saute until cooked through, then add chili sauce, stir to coat and shut off burner.
Top each slice of Ciabatta with the chicken saute, then generously sprinkle cheese on top.
Bake until the cheese is melted and bread is lightly browned.