Chex Peanut Butter Marshmallow Bars

I got this yummy kid pleaser from my mom. Sweet and salty is always a winner!
Chex Peanut Butter Marshmallow Bars

2 cups Corn Chex
2 1/2 cups stick pretzels (broken in half)
1 1/2 cups M&M's
1/2 stick of butter
1/3 cup creamy peanut butter
5 cups small marshmallows

Combine Corn Chex, pretzels, and M&M's in a large bowl. In a sauce pan melt butter and peanut butter. Add marshmallows and stir until melted. Cool slightly and pour into Chex mixture. Put in a prepared 9x13 pan and let sit and cool. Cut into small bars to serve.