Preheat oven to 350 degrees F (175 degrees C). Grease a 8x8-inch baking pan.
Cream together butter and brown sugar. Mix in egg and vanilla.
In a separate bowl, whisk flour, baking powder, and sea salt together. Gradually incorporate dry ingredients into the butter/sugar mixture. Mix thoroughly.
Stir in creamy peanut butter, oats, chocolate chips, and candy-coated chocolates. Spread mixture evenly in prepared baking pan.
Bake until set, 25 to 27 minutes. Allow to fully cool before cutting into bars.