- Preheat oven to 250 degrees Combine first four ingredients in a large, sprayed with Pam,  foil turkey roasting pan; toss gently and set aside. 
-  Melt butter in large saucepan (non-stick if you have one); stir in brown sugarand corn syrup. 
-  Bring to a boil over low heat stirring constantly. 
-  Once boiling cook without stirring for 5 minutes. 
-  Remove from heat. 
-  Stir in vanilla and baking soda ( A chemical reaction will happen as you are stirring in the vanilla and baking soda).  
- Pour over popcorn mixture; stir until mostly coated. 
-  Bake at 250 degrees for one hour stirring every 15 minutes.  
- Cool and break apart and store in airtight containers like clear food bags. 
- Notes:  Measurements for Rice Chex and Cheerios Cereals doesn't have to exact. Start with 2 cups each and then add more of each to fill the pan.Tidbit Tip: After popcorn has cooled in turkey pan place your arms around the pan and bend turkey pan in all directions to help break up the popcorn scramble for bagging.  Enjoy.  It will be the best you ever made!