Heat oven: Preheat to 350°F (175°C). Line two baking sheets with parchment.
Prep ingredients: Make sure butter and eggs are at room temperature for even mixing.
In a medium bowl, whisk 1 1/4 cups flour, 1 1/2 cups rolled oats, 1 teaspoon baking soda, and 1/2 teaspoon salt until combined.
In a large bowl, beat 1/2 cup unsalted butter with 3/4 cup light brown sugar and 1/2 cup granulated sugar until light and fluffy, about 2 minutes.
Beat in 3/4 cup creamy peanut butter until smooth.
Add 2 large eggs, one at a time, then 2 teaspoons vanilla. Mix until glossy and combined.
Add the dry ingredients to the wet and mix on low just until no streaks remain. Do not overmix.
Fold in 3/4 cup chocolate chips, 3/4 cup chocolate chunks, and 3/4 cup candy-coated chocolates. Reserve a small handful of each for topping.
Use a 3-tablespoon scoop (heaping cookie scoop) to portion dough onto prepared sheets, spacing 2 inches apart.
Press a few reserved chips, chunks, and candies onto the tops for a bakery look.
Bake 10–12 minutes until edges set and centers look slightly underdone. They’ll finish on the sheet.
Cool on the pan 5–7 minutes, then move to a rack. The cookies will set up soft and thick.
Pull early: Take cookies out when the centers still look a touch glossy.
Pan rest matters: That 5-minute rest on the hot sheet finishes the bake without drying the centers.
Weigh if you can: Accurate flour and oats make the difference between soft and dry.
Use no-stir peanut butter: Natural peanut butter separates and changes texture.
