In the middle of the Gettysburg Campaign, Pleasonton reorganized his corps and Gregg now commanded the 2nd Division. He led it in cavalry engagements at Aldie, Middleburg, and Upperville. While his fellow, newly promoted division commander Brig. Gen. John Buford was initiating the Battle of Gettysburg on July 1, 1863, Gregg was still moving north. His division arrived mid-day on July 2 and took up positions to protect the right flank and rear of the Union Army. On July 3, Three miles east of Gettysburg, in what is now called "East Cavalry Field", Stuart's forces collided with Gregg's division and Brig. Gen. George A. Custer's brigade of the 3rd Division. A lengthy mounted battle, including hand-to-hand combat, ensued. Both sides claimed victory. After the battle Gregg took his division to Chambersburg Pa, and did not participate in the Cavalry pursuit of the Army of Northern Va.