Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper or lightly grease them.
Cream the butter, granulated sugar, and brown sugar in a large mixing bowl until light and fluffy.
Add the egg and vanilla extract and beat until smooth.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add to the creamed butter mixture until combined.
Stir in the oats until evenly distributed.
If using gumdrops, cut them into small pieces and toss lightly in flour to prevent sticking.
Fold the gumdrops (or candy) into the dough until just combined.
Drop 2-inch cookie scoops of dough onto the prepared baking sheets, spacing 2 inches apart.
Bake for 13-15 minutes, until edges are golden but centers are still soft.
Cool on the baking sheet for 2 minutes, then transfer to a wire rack to cool completely.
