Preheat the oven to 350 degrees.
Line a baking sheet with parchment paper and set aside.
In a large bowl, combine the rice, corn, and wheat cereal varieties along with the nuts and pretzels. Toss to combine.
In a small, microwave-safe bowl, melt the butter.
Add the Worcestershire sauce, seasoned salt, granulated garlic, and onion powder. Whisk to combine.
Pour the butter mixture over the cereal mixture and toss until well coated throughout.
Spread the coated mix on the prepared baking sheet in an even layer.
Bake for 30-40 minutes - stirring once after 15-20 minutes.
Remove from the oven and allow to cool to room temperature before serving or transferring to an airtight container.