Gastrointestinal endoscopy is a subjective procedure that frequently requires tissue samples for diagnosis. Contact optical biopsy (OB) techniques have the aim of providing direct diagnosis of endoscopic areas without excising tissue samples but lack the wide-area coverage required for locating and resecting lesions. This article presents a large-area robotically deployed OB imaging platform for endoscopic detection of colorectal cancer as an add-on for conventional endoscopes. In vitro, in silicon colon phantoms, the platform achieves an optical resolution of 0.5 line pairs per millimeter, while resolving simulated cancer lesions down to 0.75 mm diameter across large-area images (55-103 cm2). Large-area OB images were generated in an ex vivo porcine colon. The platform allows centimeter-sized large-area OB imaging in vitro and ex vivo with submillimeter resolution, including automatic data segmentation of simulated cancer areas. The ability for robotic actuation and spectrum collection is also shown for ex vivo animal colon. If successful, this technology could widen access to user-independent high-quality endoscopy and early detection of gastrointestinal cancers.