Heat pinto beans in a saucepan over low heat until hot, 5 to 7 minutes.
Bring water, quinoa, and salt to a boil in a saucepan and simmer until quinoa is tender and water is absorbed, 15 to 20 minutes. Remove from heat and set aside to cool, about 10 minutes.
Heat olive oil in a skillet over medium heat. Add red bell pepper, yellow bell pepper, and black pepper; cook and stir until bell peppers are softened but still crisp, about 10 minutes.
Toss quinoa, pinto beans, and lettuce together in a bowl. Top with pepper mixture, vegan cheese, avocado, and vegan sour cream.
