Arriving at the Rappahannock, the 61st was assigned to defending Freeman's Ford as the Army of Virginia and the Army of Northern Virginia each looked for a chance to cross the river and strike the other. On August 22 General Sigel ordered a reconnaissance at Freeman's Ford and the 74th Pennsylvania under Colonel Alexander Schimmelfennig crossed the river. On reaching the other side Schimmelfennig found the Confederates under Major General Thomas Jackson marching north away from the ford. Schimmelfennig believed that he could strike the rear of Jackson's force and capture Jackson's wagons if the 74th Pennsylvania was reinforced. The 61st Ohio and 8th West Virginia crossed the Rappahannock and joined the 74th Pennsylvania in a woods near the rebel wagons. Before they could reach the wagons though, the Federals were suddenly attacked by a Confederate brigade which had been left behind to protect the supplies. The Confederates under Brigadier General Isaac Trimble forced Bohlen's brigade back through the woods and towards the Rappahannock. The retreat began in good order but soon turned into a rout as two brigades from Brigadier General John Hood's division joined the fight. Many of the Federals did not cross the river at the ford but instead jumped into the river wherever they could and swam across. The brigade reformed on the Union side of the Rappahannock as Federal reinforcements arrived. However the Confederates did not press the attack and the engagement ended.
The 61st suffered 12 casualties, including 6 killed, at Freeman's Ford. Also killed was General Bohlen. Shot while trying to rally his brigade, Bohlen was replaced by Colonel Schimmelfennig of the 74th Pennsylvania. While Freeman's Ford may have been an inauspicious start for the 61st, the regiment would soon have a chance to redeem itself. On August 29 the 61st took part in Pope's attack on Jackson near Manassas, Virginia.
At 11 a.m. on August 29 Schimmelfennig's brigade was ordered to attack the left flank of Jackson's line, in support of Schurz's second brigade which had attacked earlier in the morning. After crossing the Sudley Road the brigade struck Brigadier General Maxcy Gregg's South Carolina Brigade, which was positioned in front of an unfinished railroad embankment. After a fierce fight the Confederates fell back to a knoll and the 61st Ohio and 74th Pennsylvania followed in pursuit. The two Federal regiments managed to advance across the railroad embankment and into a cornfield before the knoll. However, Gregg received reinforcements and the 61st Ohio and 74th Pennsylvania retreated back to the unfinished railroad. The battle now became a stalemate as Sigel and Schurz awaited reinforcements to continue the attack. However, by early afternoon it became apparent that no Union reinforcements would be helping and so Schurz's division was pulled back to the main Union line.
The 61st remained in reserve for the rest of the battle as Pope continued his piecemeal attacks on Jackson. On the evening of August 30 the 61st, with Captain Hubert Dilger's Battery I, 1st Ohio Light Artillery, formed the rear guard as the Army of Virginia retreated to Centerville on the road to Washington. The 61st encamped near Fairfax Courthouse where it would spend the next couple of months guarding Washington.
The regiment would need the time to reorganize. Besides the 35 men killed, wounded, or captured, the 61st also faced a crisis in its officer corps. Like many Civil War units, cliques of officers competed in the 61st with some of the officers loyal to Colonel Schleich and others loyal to Lieutenant Colonel McGroarty. The issue became public during the Second Bull Run campaign as Colonel Schleich and a number of other officers mysteriously disappeared from the regiment. Lieutenant Colonel McGroarty pressed for an investigation and in the weeks that followed Colonel Schleich and 12 other officers either resigned or were discharged. In October McGroarty was promoted to Colonel and began filling the vacant officer positions.
