Since plant protein is generally accepted as sustainable and environmentally friendly, production of new plant protein-based products is expanding and a raw material is diversified to ensure a high-value and complete meal. The objective of the study was to compare chemical composition and amino acid provision of pea-buckwheat, pea-barley and pea-oat extruded mixtures with the aim to look for new products to diversify diet using the best plant protein resources. Within the research, amino acid scores of hull-less barley, buckwheat, hull-less oat and grey pea as an indicator of raw material protein quality were evaluated. The highest scores of essential amino acids were found in oat and pea protein. Amino acid scoring patterns of raw material – oat ‘Stendes Emilija’ and grey pea ‘Bruno’ fully meet the requirements for essential amino acid supply. The protein of buckwheat is the richest in lysine (4.3 g 100g−1 protein) among studied cereals, although the difference in the essential amino acids was not significant. The results of the research showed that pea-barley and pea-buckwheat composite mixtures meet human needs better if pea protein is used in the proportion 65:35 with barley or buckwheat flour than in the proportion 35:65. The high protein content – 43.33% and 43.96%, the sum and composition of essential amino acids, and high level of total dietary fibre – 11.9% and 13.7% are the main reasons to consider the mixtures (including as a base for smoothies) as a complete meal.