Here's the first in a series of pumpkin pie recipes from old advertising.
Impossible Pumpkin Pie
recipe from 1980s Bisquick advertising
3/4 cup sugar
1/2 cup Bisquick baking mix
2 tbsp. butter
1 can (10 oz.) evaporated milk
1 can (16 oz.) pumpkin
2 1/2 tsp. pumpkin pie spice
2 tsp. vanilla
Heat oven to 350˚. Grease pie plate, 9 x 1 1/4 or 10 x 1 1/2 inches. Beat all ingredients until smooth, 1 minute in blender on high or 2 minutes with hand beater. Pour into plate. Bake until knife inserted in center comes out clean, 50 to 65 minutes.
High Altitude: Heat oven to 375˚. Bake 45 to 50 minutes.
I don't know about your grandmother but mine didn't use baking mixes. She made crusts from scratch. With lard. And they were amazing.