Inclusion Criteria:  History of allogeneic hemopoietic stem cell transplant in the past 100 days Post-engraftment, defined by three consecutive days of sustained neutrophil engraftment with an absolute neutrophil count of at least 500 cells/mm^3 Moderate to severe acute GI GvHD stage 2 or higher as measured by the modified Glucksberg criteria and averaged over 3 consecutive days. In patients who have already had GI biopsy, biopsy histology must be compatible with GVHD, although biopsy is not required  Exclusion Criteria:  History of previous serious adverse events associated with FMT History of bowel perforation History of bowel resection History of intestinal obstruction History of gastric bypass History of diverticulitis History of inflammatory bowel disease (i.e. Crohn's disease and ulcerative colitis) History of celiac disease confirmed by serologic testing or small bowel biopsy History of severe dietary allergy as designated by World Allergy Organization Subcutaneous Immunotherapy Systemic Reaction Grading System grade 2 or more Current evidence of mechanical obstruction of the bowel Known allergies to sodium chloride, glycerol, theobroma oil, hide bovine gelatin, sodium lauryl sulfate, colorants FD&C, or titanium dioxide Currently pregnant, planning to become pregnant or breastfeeding during the study period. Women of childbearing potential (those who are not post-menopausal or post-hysterectomy) must be negative for pregnancy per urine pregnancy test at enrollment Individuals with the ability to conceive children who are not willing to abstain from sexual activity or use an effective form of birth control during the duration of the study Unwilling or unable to participate in study procedures including oral intake of FMT, colonoscopy, fiber supplementation, collection of stool samples and completion study surveys Cannot reasonably and safely participate in the study in the opinion of the investigators