Preheat the oven to 350°F (175°C).

Line a baking sheet with parchment paper.

In a large mixing bowl, combine the Rice Chex, Corn Chex, pretzels, and nuts.

Melt the butter in a saucepan over medium heat.

Stir in the brown sugar and corn syrup into the melted butter.

Remove from heat and mix in the vanilla extract and baking soda.

Pour the butter mixture over the dry ingredients and stir until evenly coated.

Spread the mixture evenly on the prepared baking sheet.

Bake for 20 minutes, stirring halfway through to ensure even crispiness.

Let the Chex Mix cool completely before storing.