As the international poultry industry searches for antibiotic alternatives, dietary probiotic supplementation has exhibited the ability to decrease FCR, increase live weight gain, and regulate inflammatory responses within the gut of broiler chickens. The in ovo (or in egg) supplementation of probiotics has the potential for promoting early colonization of probiotic bacteria in the gastrointestinal tract and providing enhanced protection against pathogens in the hatchery and grow-out facilities. In the present studies, the in ovo injection of either L. animalis + E. faecium combination or L. animalis + B. licheniformis combination on d 18 of incubation does not negatively affect the chick’s ability to hatch out of the egg. These combinations also influence post-hatch performance, where FCR, gastrointestinal tissue weights, and immune-physiological parameters were impacted under non-challenged and coccidiosis-challenged grow-out conditions. These results indicate the physiological and immunomodulatory role that beneficial bacteria may have on a developing chick.