This 42-d experiment investigated whether the growth performance response of broiler chickens receiving reduced-protein (RCP) diets and challenged with coccidiosis was influenced by partly replacing soybean meal (SBM) with alternative plant protein feedstuffs. A total of 1,176 male chicks received an adequate protein (ACP) starter diet from d0to8.Ond8,thebirdswereallocatedto4dietsina randomized complete block design. These were a corn-SBM ACP diet, corn-SBM RCP diet (RCP-SBM), RCP diet with 80 g/kg canola meal (RCP-CM), or RCP diet with 100g/kg cDDGS (RCP-cDDGS). All the RCP diets had 30 g/kg protein below the ACP diets in their respective phases (but similar standardized digestible amino acids and dEB). On d 15, each diet was further divided into two groups (with or without mixed Eimeria spp. challenge) for a total of 8 treatments (2×4 factorial), and 7 replicates each. Birds and feed were weighed on d 8, 14, 21, 28, and 42. A gut permeability test was done for one randomly selected bird/replicate on d 21 (6 d post-challenge) using FITC- dextran. Caecal content on d 42 were analyzed for short- chain fatty acids (SCFA) profile. In the pre-challenge phase (d 8 to 14), birds receiving the RCP-CM diet had lower weight gain than the ACP diet (P < 0.05). During the active Eimeria infection (0 to 7 d post-challenge), there was a significant diet × cocci (P < 0.05) where the feed intake was greater for birds receiving ACP than other treatments in non- challenged groups. In the challenged groups, birds receiving RCP-CM and RCP-cDDGS had greater (P < 0.05) feed intake than ACP and RCP-SBM diets. The challenged group had lower weight gain and higher FCR (P < 0.05) during this period. There was no diet × challenge on the overall (d 8 to 42) growth performance. The overall weight gain and d 42 body weight tended to be greater (P < 0.10) for ACP than the other treatments. During this period, Eimeria-challenged birds had lower weight gain and greater FCR (P < 0.05). The gut permeability test on d 21 (6 d post-challenge) showed no significant diet effect. There was significant diet × cocci (P < 0.05) for isobutyrate and isovalerate (P < 0.05) with no diet effect in the unchallenged group, whereas in the challenged group, RCP-CM had lower (P < 0.05) isobutyrate than ACP diet; and both RCP-SBM and RCP-CM treatments had lower (P < 0.05) isovalerate than ACP. The challenged group had lower (P < 0.05) acetate and butyrate than the non- challenged group.