Monster cookies are everything good that there is about cookie-baking and candy-eating. These classic cookies are loaded with peanut butter, oats, chocolate chips, and M&Ms; they bake up soft, chewy, and thick, and are absolutely irresistible!
Preheat the oven to 350 degrees F. Line three baking sheets with parchment paper.
In a large mixing bowl, stir together the eggs, both sugars, vanilla extract, baking soda and salt. Then stir in the melted butter and peanut butter, followed by the oats and flour. Lastly, stir in the chocolate chips and M&M's. Let the dough rest (at room temperature) for 30 minutes.
Drop the dough by ¼ cupfuls onto baking sheets. Use your fingers to flatten the dough slightly. Baking for 15 to 17 minutes, or until the cookies are a light golden brown. Let cool on the baking sheet for 5 minutes, then remove to a wire rack and cool completely. Store in an airtight container at room temperature for up to 5 days.
Nut Butter Alternatives - You can use other nut butters such as almond butter, cashew butter, etc. as long as they do not have oil separation (see the note above). A great almond butter substitute that works exceptionally well in all baked goods I've tried it with is Barney Butter.
Mix-Ins - You can customize these cookies with different baking chips, candy, dried fruit, cereal, nuts, etc. See post above for specific suggestions.
Troubleshooting - See post above for solutions to common issues such as cookies spreading too much or too little, being crumbly, and overbaking.
Make-Ahead - You can prepare the cookie dough and refrigerate for up to 3 days before baking. When ready, let it sit on the counter for about 30 minutes before scooping and proceeding with baking.
Storage - These cookies will keep in an airtight container at room temperature for up to 1 week.
Freezing Instructions - Freeze the baked cookies by wrapping them individually in plastic wrap, then place them in a ziptop bag and freeze for up to 3 months.
Freezing the Dough - You can roll the dough balls and freeze them for up to 2 months. Bake for an extra minute or so.