Rosalie,
I have not eaten IHOP's harvest grain pancakes & I have not tried this recipe. I hope it is what you are looking for.

IHOP's harvest Grain Pancakes
Mix:
7 3/4 cups of all-purpose flour
1 1/8 cups of Quaker Quick Oatmeal
1 1/2 cups of whole wheat flour
3 1/2 cups of corn meal
1 cup wheat bran
3/4 cups of sugar
1 1/3 cups of finely chopped pecans
5 3/4 TBSP baking powder
2 1/2 tsp baking soda
2 1/3 TBSP dry malt
1 3/4 tsp salt

Mix all ingredients together. Store in air tight container.

To make batter:
2 cups of buttermilk
2 extra large eggs
2 cups of above mix
2 tsp liquid vanilla
6 TBSP butter
1 tsp water

Put buttermilk in bowl & whisk in eggs. Whisk in pancake mix. Melt butter in microwave with 1 tsp of water & whisk into batter.
This amount of batter makes 5 servings.