Background: Oral antibiotic bowel preparation (OABP) before colorectal resection has been shown to reduce surgical site infections. We examined whether OABP decreases length of stay (LOS) and readmissions for colorectal surgery. Study Design: This retrospective study used national Veterans Affairs Surgical Quality Improvement Program preoperative risk and outcomes data linked to Veterans Affairs Administrative and Pharmacy Benefits Management data on patients undergoing elective colorectal resections from 2005 to 2009. Exclusion criteria were preoperative LOS >2 days, American Society of Anesthesiologists class 5, or death before discharge. Patient and surgery characteristics, bowel preparation use, presence of an ostomy, indication for surgery, and indication for readmission using ICD-9 codes were determined. Negative binomial regression was used to model LOS. Logistic regression analyses modeled 30-day readmission. Results: Of the 8,180 patients, 1,161 (14.2%) were readmitted within 30 days. Length of stay and readmissions varied significantly by bowel preparation, procedure, presence of an ostomy, and American Society of Anesthesiologists class. Oral antibiotic bowel preparation was associated with a below-median postoperative LOS (negative binomial regression estimate = -0.1159; p < 0.0001) and fewer 30-day readmissions (adjusted odds ratio = 0.81; 95% CI, 0.68-0.97). Overall, 4.9% were readmitted for infections (ICD-9 codes) and this varied by bowel preparation (no preparation 6.1%, mechanical 5.4%, OABP 3.9%; p = 0.001). The readmission rate for noninfectious reasons was 9.3% and did not differ significantly by bowel preparation (no preparation 9.9%, mechanical 9.6%, OABP 8.8%; p = 0.38). Conclusions: Oral antibiotic bowel preparation before elective colorectal surgery is associated with shorter postoperative LOS and lower 30-day readmission rates, primarily due to fewer readmissions for infections. Prospective studies are needed to verify these results. © 2013 by the American College of Surgeons.