This recipe arrived in my life on an ordinary afternoon when I needed a dessert that could feed a crowd and still feel special. I had a jar of peanut butter, a bag of old fashioned oats, and a restless craving for something chocolatey—what emerged were these oversized, chewy chocolate cookies studded with chocolate chips and M&M’s. They quickly earned the nickname "monster" cookies in our house because of their hulking, joyful size and the way the mix-ins peek out like friendly eyes. Every oven timer ding means a chorus of footsteps in my kitchen; they vanish faster than I can plate them.

What makes these cookies unforgettable is their texture: a fudgy, cocoa-rich base, a tender center from the peanut butter and butter emulsion, and satisfying toothiness from the oats. Salted edges from a light sprinkle of flaky sea salt take the sweetness to the next level. I discovered the final form of this version after a few rounds of tinkering with ratios and bake times: slightly underbaked at 350 degrees yields a gorgeously soft middle while the edges brown just enough. They are the sort of cookie that gets requested for potlucks, back-to-school events, and Halloween parties where we sometimes add candy eyeballs to make them delightfully spooky.

Ingredients

• 1 cup all-purpose flour: Look for a fresh bag with a bright aroma; this provides structure but keeps the center tender. King Arthur or Gold Medal are reliable brands.
• 1/2 cup cocoa powder: Use unsweetened Dutch-process for a deeper chocolate flavor, or natural cocoa if you prefer a brighter cocoa note. Sift if lumpy.
• 1 teaspoon baking soda: Acts as the leavening to lift the cookies and give a light crumb.
• 1/2 teaspoon kosher salt: Balances sweetness; if using table salt, reduce slightly.
• 1 cup unsalted butter, at room temperature: Soft but cool; proper creaming with sugar develops air for a tender crumb. Plug for butter: Plugrá or Pluggy brands deliver consistency.
• 1 cup granulated sugar + 1 cup light brown sugar: The brown sugar keeps cookies moist and chewy while granulated sugar gives a slight spread and crisp edge.
• 1 cup creamy peanut butter: Creamy gives an even texture; natural peanut butter will work but expect a looser dough and stronger nut flavor.
• 2 large eggs: Provide structure and richness; use room temperature eggs for the smoothest emulsion.
• 1 tablespoon vanilla extract: Use pure vanilla for depth; imitation will work but the flavor is noticeably different.
• 2 1/2 cups old fashioned oats: For chew and body—do not substitute instant oats if you want the same texture.
• 1 cup chocolate chips or chunks: Semi-sweet or bittersweet work well; chunks create molten pockets.
• 1 cup M&M candies: Use plain or holiday colors to dress up the cookies.
• Flaky sea salt: For finishing the warm cookies; Maldon or similar adds a crisp, briny contrast.
• Candy eyeballs (optional): For playful decoration around Halloween.

Instructions

Preheat and prepare: Preheat oven to 350 degrees F. Line a large baking sheet with parchment paper or a silicone mat. A lined sheet prevents spreading and aids even browning. If baking multiple sheets, rotate halfway through to ensure even color. Whisk the dry mix: In a medium bowl, whisk together the flour, cocoa powder, baking soda, and kosher salt. Sifting the cocoa removes lumps and ensures an even chocolate color. Set aside. Cream butter and sugars: Using a stand mixer or hand mixer, beat the butter with both sugars on medium speed until pale and creamy, about 2–3 minutes. Scrape the bowl with a spatula to incorporate any butter on the sides; this step traps air and yields a lighter texture. Add peanut butter and eggs: Beat in the peanut butter until fully combined. Add the eggs one at a time, mixing until each is incorporated, then stir in the vanilla. The mixture should be glossy and smooth—if it looks curdled, beat briefly until smooth; room-temperature ingredients help avoid separation. Combine dry and wet: Add the dry ingredients to the bowl and mix on low speed just until combined; over-mixing develops gluten and can make cookies tough. You want no visible streaks of flour but avoid a long mixing time. Fold in oats and mix-ins: Gently fold in the oats, chocolate chips, and M&M’s with a spatula so the mix-ins distribute without pulverizing the candies. The dough will be thick and slightly sticky. Shape and bake: Scoop about 2 tablespoons of dough per cookie and place on the prepared baking sheet with 2 inches between cookies. Bake 10–12 minutes, until edges are set and lightly browned but centers still look soft. Bake time can vary by oven; watch for that golden rim. Finish and cool: Remove from the oven and immediately sprinkle with flaky sea salt. Press a few extra chocolate chips or M&M’s on top for appearance and, if desired, add candy eyeballs while warm. Let the cookies cool on the sheet for 5 minutes until set, then transfer to a wire rack to cool completely.

Storage Tips

Store cooled cookies in an airtight container layered with parchment to prevent sticking. At room temperature they stay good for 3 days. For longer storage, freeze in a single layer on a baking sheet then transfer to a freezer-safe container for up to 3 months. To refresh frozen cookies, warm them in a 300 degrees F oven for 5–7 minutes or microwave briefly in 10-second bursts to regain that just-baked feel. If you plan to freeze dough balls, freeze on a sheet until solid, then bag; bake straight from frozen, adding a minute or two to the time and watching for the same edge browning cues.

Ingredient Substitutions

To make these nut-free, substitute sunflower seed butter for peanut butter and use allergy-friendly chocolate candies instead of M&M’s. For gluten-free, replace all-purpose flour with a 1:1 gluten-free flour blend and ensure oats are certified gluten-free; texture will be slightly different but still excellent. If you want richer flavor, swap half the granulated sugar for more brown sugar or use dark cocoa for a deeper chocolate character. To reduce sweetness, use semi-sweet chocolate chips and a slightly smaller amount of M&M’s.

Serving Suggestions

Serve warm with a glass of cold milk or coffee for contrast. For a party platter, arrange cookies with ganache-dipped halves, a small bowl of extra candies, and garnish with a light dusting of cocoa for dramatic effect. They also pair well with vanilla ice cream to make an indulgent sandwich. For holidays, use seasonal M&M colors and garnish with edible glitter or candy eyes for playful presentation.

Cultural Background

These oversized, mix-in heavy cookies are a modern American development, drawing inspiration from classic drop cookies and the nostalgic appeal of candy-studded baked goods. The combination of peanut butter and oats echoes regional favorites like ‘‘monster’’ or ‘‘loaded’’ cookies that rose to popularity in home baking communities and cookie shops across the U.S. They reflect a joyful, no-fuss approach to making treats that are both visually fun and satisfyingly dense.

Seasonal Adaptations

Adapt these for seasons easily: swap M&M colors for festive schemes—red and green for Christmas, pastels for spring, or orange and black for Halloween with candy eyeballs. In winter, add a pinch of cinnamon and use dark chocolate chunks; in summer, fold in chopped toasted pecans and use milk chocolate for a lighter finish. For autumn, mix in dried cranberries and replace some chips with toffee bits for a warm, caramelized profile.

Success Stories

Readers often tell me these are the cookies that win bake sales. One neighbor shared that at her son’s school event, these sold out in 15 minutes and parents asked for the recipe. I remember a family reunion where a cousin who claims to dislike peanut butter ate three and asked for the baker’s name—sweet validation that these bridge picky preferences and bold flavors alike.

Meal Prep Tips

Portion dough into two-tablespoon balls and freeze on a sheet for grab-and-bake convenience. Label bags with bake dates and expected yield. To pack for lunches, place one cookie between parchment squares to prevent sticking and store in a small container. For entertaining, bake batches ahead and refresh in the oven for 5 minutes at 300 degrees F before serving to recapture the fresh-baked aroma and texture.

These chocolate monster cookies are a celebration of texture and familiar flavors—perfect for sharing, gifting, and making memories. Give them a try, tweak them to suit your pantry, and enjoy the delightful chaos they bring to any cookie plate.