Magnetotransport of high‐mobility electrons in quasi‐one‐dimensional quantum wires in Si/Si0.7Ge0.3 heterostructures is studied. Arrays of shallow and deep etched wires with a period of 480 nm are defined by laser holography and patterned by reactive ion etching. Typical features of transport in narrow electron channels, such as oscillations due to the depopulation of quasi‐one‐dimensional subbands and an anomalous resistance maximum at low magnetic fields are observed. The narrowest channels have an effective width of ≊70 nm and a sublevel spacing of 1 meV.