Cook quinoa - Combine quinoa and stock in a saucepan. Add in some salt. Bring to a boil covered. Lower heat, keep covered, and cook until liquid is absorbed, 8 to 10 minutes. (Can be done up to 5 days ahead)
Make vinaigrette - Whisk together soy sauce, vinegar, brown sugar, toasted sesame oil, and cooking oil. (Can be done up to 5 days ahead)
Cucumbers / Bell peppers - Prep as directed. Store separately. (Can be done up to 3 days ahead)
Lettuce / Clementines / Edamame - Prep as directed. If using frozen edamame, defrost. Store separately. (Can be done 1 day ahead)