Quinoa (Chenopodium quinoa Willd) is a pseudocereal of Andean origin with bioactive substances in its composition, among which phenolic compounds, known for their antioxidant properties. Quinoa can be used in the formulation of bakery products due to the technological properties of its seeds such as solubility, water holding capacity, gelation and emulsification. This study was aimed at determining the content of phenolic compounds in quinoa flour (QF), quinoa flakes (QFL) and in gluten-free quinoa-based cookies (QC) formulated and optimized among 14 formulations from an experimental design of ternary mixture. The content of phenolic compounds was determined by spectrophotometry at 760 nm using gallic acid as standard for the calibration curve. The content of phenolic compounds was expressed as mg of gallic acid equivalents (GAE) per 100 g of dry matter. The results of phenolic compounds were 99.87 ± 11.45, 76.11 ± 8.02, 27.67 ± 4.03 mg GAE / 100g for QFL, QF and QC respectively, showing losses of these phytochemicals during processing. Considering the antioxidant activity of phenolic compounds and aimed to maintain this property, the best option for consumption is the addition of quinoa flour and flakes in ready-to-eat products.