The story features three goat brothers of different sizes—Little, Middle, and Big Billy Goat Gruff. They are hungry and want to cross a bridge to reach a hillside filled with sweet, green grass.

However, a terrible, hungry Troll lives under the bridge and threatens to eat anyone who tries to cross. The brothers come up with a clever plan:

• The Little Goat: When he crosses, the Troll stops him. The little goat tells the Troll to wait for his bigger brother, who will be a much tastier meal. The greedy Troll lets him pass.

• The Middle Goat: He tells the Troll the same thing—to wait for the biggest brother. Again, the Troll lets him go.

• The Big Goat: When the largest brother arrives, the Troll jumps up to eat him. But Big Billy Goat Gruff is too strong; he uses his massive horns to knock the Troll off the bridge and into the water below.

With the Troll gone, the three brothers happily feast on the hillside until they are "so fat they can hardly walk home."