MD 135 begins at an intersection with US 219 on the eastern edge of Oakland. Northbound US 219 (Oak Street) continues straight west into downtown Oakland, southbound US 219 (Garrett Highway) heads south toward Red House, and 9th Street (unsigned MD 219) heads north along the alignment of the future Oakland Bypass. MD 135 heads east through Mountain Lake Park as Maryland Highway, a controlled access two-lane undivided highway. Oakland Drive, which is unsigned MD 825B, splits to the northeast to serve residential areas on the north side of town. The old alignment rejoins MD 135 at G Street before access controls cease upon crossing the Little Youghiogheny River. The state highway intersects MD 560 (Paull Street), which heads south into Loch Lynn Heights. After crossing the river again, MD 135 leaves Mountain Lake Park. The state highway passes scattered residences, farms, and businesses before entering Deer Park. After passing Deer Park Hotel Road, which passes the Pennington Cottage, MD 135 intersects the old alignment of MD 38, which is Sand Flat Road to the north and Main Street to the south. The state highway passes the historic home Glamorgan and Edgewood Drive, part of the old alignment of MD 38, before leaving Deer Park. Upon reaching the hamlet of Altamont, MD 495 (Swanton Road) continues straight northeast toward Swanton while MD 135 turns to the southeast.