Rainbow m&m Cookie Bars

Rainbow Cookie Bars: delicious chocolate chip cookie bars topped with a rainbow buttercream (tutorial)

I love frosting. Preferably a good buttercream frosting. And this one has rainbow colors. One of the bloggers I follow showed a tip how to make a rainbow frosting. I’ve done something similar for meringue cookies, I don’t know why I never thought to do this with frosting. Oh, the possibilities are endless now!!
*read the directions below for rainbow instructions*

I happen to love a lot of frosting. Give me a giant slice of cake, from the corner, with extra frosting please. While some of my family scrapes the extra frosting off their cake, I pile it on to my slice.

But, since I like to make my family happy, I did make some of the cookie bars with NO frosting. I’m okay with that too, it means more for me!

Unfrosted m&m Cookie Bars

Yield: 16 large bars

Rainbow M&M'S Cookie Bars

Rainbow M&M'S Cookie Bars
Rainbow Cookie Bars: delicious chocolate chip cookie bars topped with a rainbow buttercream (tutorial)


For the Cookie Bars:

  • 3/4 cup Crisco (butter flavored)
  • 1 1/4 cup brown sugar
  • 2 Tbsp milk
  • 1 Tbsp vanilla extract
  • 1 egg
  • 1 3/4 cup flour
  • 1 tsp kosher salt
  • 1 tsp baking soda
  • 1 pinches of nutmeg
  • 1/2 tsp cinnamon
  • 12oz bag of milk chocolate morsels
  • 1 1/2 cup m&m candies

For the Frosting:

  • 1 cup Butter, softened
  • 5 1/2 cup powdered sugar
  • 1/4 cup milk
  • 2 tsp vanilla
  • 1 1/2 Tbsp meringue powder
  • gel food coloring


  1. For the cookies, combine crisco, sugar, milk and vanilla. Beat in eggs. Add dry ingredients and combine thoroughly. Add in morsels.
  2. Press into bottom of baking sheet (with sides). Bake in a 375 degree oven for about 25 minutes. Center may appear to be a little under cooked, let it rest in baking pan until completely cooled.
  3. For the frosting, beat all ingredients together for 5 minutes until fluffy. Add more milk if necessary for desired consistency.
  4. To frost cookie bars with rainbow pattern, open a large (16inch) decorator bag (I used disposable). Taking your gel food coloring, make stripes from the tip of the bag up 3/4 of the way.
  5. Repeat with other colors. Spoon your frosting into the bag carefully, twist the top and secure.
  6. Cut cookie bars into desired sized pieces. Pipe frosting onto individual bars. The rainbow colors may be more pronounced with the first bars, and become lighter in color with remainder. Enjoy!

Rainbow Cookie Bars: delicious chocolate chip cookie bars topped with a rainbow buttercream (tutorial)

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27 comments on “Rainbow m&m Cookie Bars”

  1. These are so pretty!! Awesome job. I love that icing 🙂

  2. I have a couple in our house that scrape the yummy frosting off. But you are right…more for us:-) Love the fun rainbow icing!!!!

  3. Frosting or no frosting…they both look good!

  4. These are gorgeous–love that rainbow frosting!

  5. I love the rainbow frosting! It’s so pretty and looks so intricate. I don’t have the patience to do that but I really want to now seeing yours!

  6. I love that frosting! I have never seen one with meringue powder and butter. It sounds SO good. I will be trying it for sure!

  7. I love all those features! Thanks so much for hosting.

  8. I love the rainbow icing–so gorge! And M&M cookie bars are my favorite.

  9. Wonderful recipe! I thik I’ll make this for Hubby tonight to take to twork. His co-workers are chocolate chip M&M fans!

  10. They look awesome, your frosting turned out so well! I just love the technique – such an impressive result and really not too difficult 🙂

  11. Those are so pretty! Love what you’ve done with the frosting … I am not the biggest, best froster, but I think I need to try that technique. Sometime.

  12. First off: M & M cookie bars = win!
    The rainbow decoration looks great! 🙂

  13. these are too cute! i’m adding them to my to-bake list. i love all those colors! awesome recipe. 🙂

  14. These look so cool. Who knew??!! And I’m right there with you on the frosting. That’s almost the best part!

  15. What a fun spring time treat. I will definitely have to make these. Love your blog and I am your newest follower. xo

  16. Great job on this frosting, Aimee! And the bars sound fabulous. The texture looks dreamy.

  17. People who scrape the frosting off are just odd. I LOVE frosting too!

  18. These are very beautiful!
    I really like the coloring

  19. Oh, yeah…. My kids and hubby would be thrilled with these!

  20. Very interesting idea for the frosting.

  21. I love cookie bars but have never frosted them. Looks like I better frost the next batch. Great recipe.

  22. Plain M&Ms are one of my biggest weaknesses. I love putting them in cookies and bars!

  23. That looks terrific. I know my family would love this. Come visit us. We have some fantastic things to share this week.

  24. Oh my goodness these look so yummy! I followed you over from Chef-in-Training and would like to invite you to share this, and any other posts, on my link party at http://www.michellestastycreations.blogspot.com. Have a great weekend.


  25. As a child of the 70s I can never resist a rainbow, especially one as “sweet” as yours!


  26. These look so delicious! We’re so glad that you linked up to our “Strut Your Stuff Saturday.” We hope you’ll be back soon. -The Sisters

  27. These are so colorful and I love the recipe for the basic cookie bar!You are a party fave this week at the {what’s shakin’ link party} … I’d love for you to come on over, link up and grab a button!

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