This experiment was designed to trace the value of two  plant protein sources, full-fat soybean (FFSB) and corn gluten meal (CGM) as a substitutes for soybean meal (SBM) in broiler diets in three main trials. A total number of 175 one day old chicks (Arbor acres) were weighed and randomly distributed into seven groups of 25 chicks each. A control group in the first trial was fed on three diets, the starter, grower and finisher based on SBM as the main protein source. In the other two main trials, two vegetable protein sources were tested as soybean meal substitutes, the full-fat soybeans and the corn gluten meal. Each of the plant proteins were used at a maximum rate of 20% in the broiler diets. For each SBM substitute, three groups were allotted, the first for feeding the substitute along the three feeding phases; starting, growing, and finishing; while the second for growing- finishing phases and the third for finishing period only. The growth performance, body weight development, weight gain, feed intake and feed conversion efficiency were assessed. In the first group of full-fat soybeans trial, there was a slight reduction in growth rate about 8%, consuming the same amount of food as that of the control (99.4%), and eventually slightly low food conversion efficiency. In the second group, more food consumed and less weight gained and by turn more lower feed conversion efficiency. In the third group and in which FFSB feeding was limited to the finishing period, growth rate was slightly higher than the control, as also the feed intake resulting in a feed conversion index nearly equal to that of the control. In trial III, feeding of broilers on 20 % corn gluten meal during the three feeding phases of growth or during growing-finishing periods had adverse effect on the feed intake, body weight, in addition to feed utilization compared to control, while only confinement of CGM feeding to the finishing period is feasible. There were no differences in the chemical composition of carcass meat and serum total protein between different experimental groups in trials II & III and control one. It is concluded that  substitution of broiler diets with 20% heat processed soybeans during growing-finishing and finishing periods support chick performance and efficiency of feed utilization, while corn gluten meal could replace 20% of the diets in broilers during the finishing period only.