Bring water, quinoa, and chicken bouillon to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until quinoa is tender and water has been absorbed, 15 to 20 minutes. Remove saucepan from heat and cool quinoa to room temperature, about 30 minutes.
Mix quinoa, tomatoes, cucumber, feta cheese, and red onion together in a bowl. Pour Italian dressing over quinoa mixture and stir to coat.