Perhaps you are thinking of Peanut Butter Squares? The one I have is from a cookie cookbook from 1971. Since it makes a huge amount it may have been originally developed for institutional baking and, given the simple preparation method, it would be likely. These have the consistency of a chewy brownie, not like a cake brownie. I do remember making them in the late '70's for a grade-school party and all the kids loved them but I haven't made them since. Nowadays everything has to be peanut-free because there are so many children/people who are allergic to peanuts.

Peanut Butter Squares
from 1971 Farm Journal "Homemade Cookies"

Makes about 8 dozen squares (that's 96 pieces!)

6 eggs
3 C granulated sugar
1 1/2 C brown sugar, packed
1 C peanut butter (smooth or chunky)
1/2 C shortening
1 Tblsp. vanilla
4 C all-purpose flour
1 1/2 Tblsp. baking powder
1 1/2 tsp. salt
optional - 1/2 C chopped peanuts for sprinkling on top

Preheat oven to 350 F. Mix well together the eggs, sugars, peanut butter, shortening, and vanilla. Add the rest of the ingredients and mix only until dough is smooth, don't over beat. Spread out evenly on two lightly greased jelly roll pans (15 1/2"x10 1/2"x1") or three (yes 3!) 13"x9"x2" pans. Sprinkle with peanuts if desired.
Bake for 25 minutes. Cut into 3" squares and cool in the pans on a rack.

Nancy

1 cup sugar
1 cup light corn syrup
1 1/2 cups peanut butter
6 cups cornflakes

Bring sugar & corn syrup to a boil. Boil 1 minute. Remove from heat, add peanut butter, stir until dissolved. Add cornflakes. Drop on waxed paper.

PEANUT BUTTER CANDY

3/4 c. powdered milk
1/2 c. honey
3/4 c. peanut butter
1 tsp. vanilla

Mix peanut butter, honey and vanilla. Blend in powdered milk, using hands when mixture becomes stiff. Pat into 8-inch square baking pan. Chill. Cut into squares.

Peanut Butter Brownies

1 cup peanut butter
2/3 cup margarine or butter
1 1/3 cup sugar
1 cup packed brown sugar
4 eggs
2 cups flour
2 tsp baking powder
1 tsp salt
Chocolate Frosting
Grease 9x13 pan. Mix peanut butter & margarine till creamy. Gradually add sugars, beating until fluffy. Beat in eggs, one at a time, until well mixed. Set aside. In another bowl, stir together flower, baking powder and salt. Gradually stir flour mixture into peanut butter mixture until well blended. Bake at 350 ° for 35 to 40 minutes. (Until a toothpick inserted comes out clean.)
Cool and frost with chocolate frosting. (I use the ready-made frosting found in the cake section of the store.)