Preheat oven to 350°. Grease a 9” x 13” pan.
Stir together oats and hot water in a mixing bowl. Cool to room temperature. Mix in sugar, cocoa, butter, and eggs. Stir in vanilla. Slowly add the flour and baking soda. Beat well. Stir in chocolate chips.
Pour mixture into prepared pan. Bake until a toothpick inserted comes out clean, about 25 to 30 minutes. Cool, dust with powered sugar, and cut into squares.