Monster Cookie Bars

Thanks to the new installment in a book series by one of my favorite authors ever*, I have no time for cookies these days. Well, maybe just day, as in the singular, since I happen to be a compulsive reader and probably will not put the book down until it’s finished, even if that means going without a shower (sorry, ew) and chopping up apples for the kids’ after school snack single handedly (talented am I). It goes without saying that my entire family is hoping that truly this book is read and put away within 24 hours.

To thank them for unselfishly allowing me to forget about reality for a while, I made them these monster cookie bars. Because, like I said, I have no time for actual cookies. Bars it is! And thankfully, they are as delicious as their cookie counterpart and much quicker than taking all afternoon to alternate pan after pan of cookies in and out of the oven (I’m glaring at you; all of you with double oven capabilities, oh yes I am).

Monster Cookie Bars

Believe it or not, transitioning a cookie recipe to a bar cookie recipe isn’t always as easy as piling the entire batch of cookie dough into a 9X13 and calling it good. So after a few little adaptations, monster cookie bars were baked, monster cookie bars were not cooled, monster cookie bars were sliced and monster cookie bars were devoured (they’ll be a bit prettier than the pictures if you wait until they cool to cut them but obviously, we.could.not.wait, and what’s so terribly wrong with an ooey, gooey, peanut buttery, chocolatey cookie bar?).

And that’s all I have to say about that because did I mention? There’s a book that needs me.

*Many moons ago, I stumbled across a Juliet Marillier book by chance in the dark abyss of my local library and after years of insisting I would never read fantasy literature, I was instantly converted (although her books are the only fantasy books I love so I guess I’m a Marillier fan not necessarily a fantasy fan; am I making any sense?). Her storytelling talent and ability is unparalleled. I love her (er, her books) so, so much. Her style may not be for everyone (as in, don’t send me hate mail if you don’t like them pretty please) but they are fabulous enough that I wouldn’t be a good friend if I didn’t share. Need a place to start? The Sevenwaters Trilogy. Right now I’m reading her Caller series. But really, enough talking already! My reading-hobby-that-is-no-more-because-of-blogging is being resurrected for a little while. Peace out.

Monster Cookie Bars

Monster Cookie Bars

Yield: Makes a 9X13-inch pan of bars

Monster Cookie Bars

It's normal for some of the M&M's to crack while baking. If you want to avoid that, you can add them to the top after you take the bars out of the oven but they won't sink into the top quite as well.


  • 2 large eggs
  • 2/3 cup granulated sugar (5 ounces)
  • 2/3 cup packed light brown sugar (5 ounces)
  • 1/4 teaspoon salt
  • 1 teaspoon vanilla extract
  • 1 cup creamy peanut butter (9 ounces)
  • 1/3 cup butter (5 1/3 tablespoons) softened to room temperature
  • 1 1/2 cups (9 ounces) chocolate chips
  • 1 teaspoon baking soda
  • 3 cups quick oats (12 ounces)
  • 1 cup M&M's (7 ounces)


  1. Preheat the oven to 350 degrees F. Grease a 9X13-inch baking pan with cooking spray.
  2. In a large mixing bowl, combine the eggs and sugars. Mix well. Add the salt, vanilla, peanut butter and butter. Mix until creamy and well combined. Stir in the chocolate chips, baking soda and oatmeal. Mix well.
  3. Spread the batter into the prepared pan and press lightly into an even layer. Sprinkle the M&M's evenly across the top and gently press them into the dough.
  4. Bake for 20-25 minutes until the edges are golden and set. Let the bars cool completely in the pan. For a cleaner cut, refrigerate the bars before slicing and serving.

Recipe Source: adapted from this Monster Cookies recipe

64 Responses to Monster Cookie Bars

  1. Sarah says:

    Can you freeze these?

  2. NAnderson says:

    I made these for the first time last night and they were SO good! I was expecting “just” a cookie bar, but the combination of peanut butter, chocolate, and oatmeal was way better than I anticipated!

  3. Kerry says:

    Thank you for a great recipe, this is the first one of yours I have cooked and it won’t be the last. One question….. I live in the UK so measured a lot of things in ounces although used cups for the choc chips. I had regular rolled oats so gave them a quick whizz in the food processor first to break them down. When I combined them with the mixture it ended up very stiff and was hard to smooth out in the tin. Is this normal? They tasted delicious and the group of 7 & 8 year olds I fed them to after a swimming lesson loved them. I may also have had a sneaky taste too 🙂

    • Mel says:

      Hi Kerry – it sounds like maybe the oats were ground slightly too much – the mixture shouldn’t be overly stiff although I guess, if they turned out well, it probably doesn’t matter. I hope you enjoy any other recipes you try!

  4. Caroline says:

    Made these this afternoon with my daughter. My family couldn’t wait for them to cool and dove right in!! Super easy and yummy:) Thanks Mel!

  5. Coby Nyd says:

    Tried these last week & couldn’t stop eating them. PB…Chocolate…Chewy oats. Need I say more?! Anyone I shared these yummy treats with loved them too! Have made 2 batches in one week(you can always come up with a reason to bake!). Thanks Mel for yet another great addition to my recipe ‘arsenal’.

  6. Heidi says:

    I am taking a meal to a gluten free new mom this week.. was planning to take these and thought all the ingredients are gluten free. But I see some comments about ‘easily made gluten free’ so that’s making me question it?

    • Mel says:

      Hi Heidi – I think what those comments are referring to is the fact that not all oats are gluten-free. Just look for oats at the store labeled gluten-free and you should be good.

  7. Anna says:

    Made these yesterday to take in our snack bag to Disneyland! Along with your peanut butter granola! My 2 year old thinks Mickey will love these! There may not be any left for Mickey, they may be devoured on the plane ride!

  8. Stacy W says:

    Made these this weekend. Another great recipe! Thanks Mel!

  9. DeDe C. says:

    Oh. My. Word. Best Saturday Night Kids In The Basement So I Can Actually Get A Bite First Treat EVER!

  10. Becca says:

    You don’t like fantasy except for Juliet Marillier books?? Not even Harry Potter? 🙂

  11. Those look SO good! Thanks for sharing!

  12. KT says:

    I was so excited to see that these are easily gluten free. I must never looked at your Monster Cookie recipe (I usually skip your sweets that will take much effort to convert…). We tried these this weekend and they are fantastic! Thank you!!

  13. Dawn says:

    I just made these and they turned out really good. They were so easy and very yummy. My boys loved them!

  14. Allison says:

    Just made these with my two year old (who kept trying to sneak chocolate chips out of the bag and lick the bowl). They are cooling now and look delish! Can’t wait to take a bite. Also, I loved how easy they were to make, much easier than cookies. Thanks, Mel! 🙂

  15. juanita says:

    I was excited to see one of my favorite cookies in bar form! I made these yesterday and they’re as delicious as they look in your picture! So far all your recipes I’ve tried have turned out wonderful!

  16. Bridget says:

    I just made these bars, the kids were so excited to see them when they got home from school!! I cut what was leftover and put them in the freezer, they will make great snacks to bring to school. Thank you for a great recipe.

  17. Somehow I didn’t even realize these were GF until I saw the comments. What is the texture of them? Similar to an oatmeal cookie, heartier?

  18. Amber says:

    These were fantastic!! Thanks for another great recipe, Mel! 🙂

  19. Angela says:

    Made these today (minus the m&ms because I don’t like them) and they were great.! Surprised how good they were with no flour in the recipe. Yum!

  20. Ali says:

    I will be making these today! And I’m pretty excited about the book recommendation too!!

  21. I am a heavy duty reader also. So I am with you, Reading Sister. These monster bars still need to be given appropriate praise anyway—–even if they were made to serve a larger purpose. I would think these would be very popular at bake sales. I will have to check out Juliet.

  22. Kim in MD says:

    I love it when I read a book that I just can’t put down! Monster cookies are awesome, and I am so excited that you have perfected them in a bar form!

  23. Best looking bars ever! So good!

  24. Meghan says:

    This post made me happy, since I, too, LOVE Juliet Marillier’s books. I only wish there were more of them!! I absolutely love your blog, and every time I see something on Pinterest or in my email with your name on it, I KNOW it will be amazing and don’t even hesitate to pin it. I really appreciate that you take the time to post tried and true recipes. Jealous you already have the new Caller book!

  25. Julie says:

    These bars look amazing!! AND I feel the same way about Marillier. She is the only fantasy author I read and I LOVE, LOVE, LOVE her books. I have read almost all of them and the Sevenwaters Trilogy is definitely my favorite (:

  26. Julia Hallo says:

    They look yummy! I loved Wildwood dancing. Could pass on the rest. . . I could never quite get into them for some reason.

  27. Susan says:

    I read books exactly the same way, I warn my husband or send a text and let him know I found a new book, can’t wait to try your suggested author. Although I like some fantasy. Another good one I just read recently is Gift of the Phoenix by Donna Cook, I loved it.

  28. I’ll have to check out that author! I love finding new ones! I just started reading Sarah Dessen’s books and absolutely love them. They are not fantasy or anything, but I highly recommend her works!

    And these bars – YUMMM!!!

  29. janene says:

    m&m’s just went on my grocery list. Thanks! My kids thank you in advance as well. 🙂

  30. Megan says:

    Um, so my comment is about the book, not the food, although the cookie bars look super good. I just have to say, I LOVE Juliet Marillier! I didn’t realize she was such a prolific author. I’ve only read her young adult books, Wildwood Dancing (one of my all time favorite retold fairy tales) and Cybele’s Secret. I can’t wait to read some of the others now that I know they exist.

  31. deborah says:

    Do you have a version of the Monster Bars with a substitute for the oats ?

  32. Kris says:

    I made bars from a monster cookie recipe, because I, like you, didn’t want to sit around all day making cookies. Well, they were done on the outside and gooey in the inside, so ended up cutting off the outside and putting it back in the oven! What a mess! I’ll definitely try these…wasn’t sure what to do to convert cookies to bars. Have you ever substituted coconut oil for the butter? It’s something I’m going to try.

    • Mel says:

      Hey Kris – I haven’t substituted coconut oil but think it would work well – I’ve been subbing it more and more in recipes that call for butter and it usually works great.

  33. I love that you can escape for a day to just read. And then that you come back thanking your family with m&m bars! Sounds like a win all around really!!

    Luci’s Morsels – fashion. food. frivolity.

  34. Angie L. says:

    Just wondering – could I substitute regular oats for the quick oats? Should I some of them first so they are smaller??? Thank you!

    • Mel says:

      Angie – I think so. I haven’t tried it but especially in bar form, it should be just fine (in cookie form, it might cause the cookies to spread a bit more). Good luck if you try it!

      • Michele says:

        I inadvertantly tried the Rolled Oats (I read the instant part after already mixing in.) It worked just fine. They hold together and aren’t too crumbly. Oh and did I mention delicious? My family devoured the pan and look forward to having it on the regular cookie rotation. Thanks Mel!

      • Angie L. says:

        I printed the recipe out to bake, then remembered I didn’t have quick oats. I just remembered tonight that I’d asked if you thought they would work! I made your chocolate chip cookies instead! They really are perfect.

  35. These look amazing and sweet 🙂 Yum!

  36. Jeanne says:

    Hi Mel – Thanks for your great writing and delicious recipes. I enjoy both!

  37. S.P.Bowers says:

    Just have to say I’m a huge Juliet Marillier fan!

  38. Alison says:

    I, too, am someone who reads but generally doesn’t read fantasy, but I also enjoyed reading Juliet Marillier’s Sevenwaters series. I will add, though, that my daughter (and my son!) and I loved Tamora Pierce’s series starting with Alanna: The First Adventure.

    These Monster Cookie Bars look scrumptious, and I like that they contain peanut butter and oats — makes them slightly less guilt ridden! Can’t wait to try! Thanks for all the terrific recipes and ideas, Mel!

  39. Jocelyn says:

    My 14 year-old daughter (ninth grade) loves fantasy books. Would Juliet Marillier’s books be suitable for this age group? Thanks!

    • Mel says:

      Hi Jocelyn – most of her books (like the Sevenwaters Trilogy and others) are geared toward an older age group than teenagers, I think, but she has two YA series (Wildwood Dancing + the Sequel, which I think would be appropriate) and the Shadowfell Series (that’s the one I’m reading now, except not right this second obviously since I felt guilty not responding to comments!). That series is a bit more serious and complicated and not as lighthearted as many YA series (although it doesn’t have crude language, immoral content, etc. so far) but might be a good fit depending on what she likes to read. You might read them first just to be sure. I’d hate to recommend something that didn’t go over well! 🙂

  40. Julie says:

    Yum! I just saw my monster cookies recipe and am excited to try these in bar form. Thanks for the book recommendation, too!

  41. tracy dickinson says:

    i am so excited!!! these are gluten free assuming gf oats are used!!! cookies with gluten free flour, while not terrible, are not my favorites! can’t wait to try these! your recipes never disappoint!!

  42. Amanda says:

    Looks like a perfect snack for this weekend! 🙂

  43. Cyndee says:

    Totally tickled that I can make easily make these gluten free! 🙂 Target has M&M’s on sale this week. Guess I know what part of one bag will be used for! Can’t wait to make them!!

  44. Becky says:

    I’m totally with you on the whole getting sucked into a book thing, although my author of choice is John Grisham. My husband refers to himself as a John Grisham Widow when I get a new book 🙂

    I have a cookie recipe that I’ve been wanting to make into a bar cookies, because sometimes cookies are just so high maintenance! Do you have any general tips for converting cookies to bars?

    • Mel says:

      Hey Becky – I wish I had a good rule of thumb. I usually just tweak them a bit because on most accounts, it’s simply that the batch of cookie dough is too large for a 9X13-inch pan. So for this recipe, I cut almost everything down by 1/3. Generally, if a cookie recipe has more than 2 1/2 to 3 cups dry ingredients, I try to scale it back a little otherwise the insides are gooey and the outside edges are charred while baking.

  45. Heather bell says:

    Those sound great especially with the high of 55 degrees tomorrow. I am always up for new books though I told myself I wasn’t going to get anything new until I finished the ones in my home library, then I picked two good ones from the library;)

  46. Mmm such a yummy bar! These sound great!

  47. I’m glad you are making time to read, Mel! As for me, I’ve had three books from the library sitting on my nightstand for two weeks, and haven’t cracked open any of them. I appreciate your author suggestion and might have to give fantasy a try. With bar cookies. 🙂

  48. I just made the cookies. I will be trying this version. My kids will love them!

  49. Carlie says:

    I LOVED Daughter of the Forest! I need to read more of the Sevenwaters series.

  50. Julia says:

    We can’t take peanut butter to school here, I wonder if one of the soy based butters would work as well???

    • Mel says:

      Hi Julia – certainly worth a try although I haven’t tried any of the other non-nut butters myself. I’m not familiar with their consistency and how they do while baking. Sorry I’m not more help!

    • Marissa says:

      We use sunbutter in place of peanut butter all the time–baking and otherwise. It isn’t 100% the same but close enough that we do it all the time. I like sun butter much better than the soy butters.

  51. Yum! Putting on the list for the kids. They would devour ém.
    Have a great day Mel!

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