The theory of electron and positron channeling and radiation production in crystals has been extended to macroscopic‐scale systems. The new theory, named QCP theory (quasi‐channeling phenomenon), examines macroscopic systems that exhibit periodicity along the axis of beam propagation, specifically, periodic electrostatic fields; the dimensions of the field periodicity (lz) are much greater than typical interatomic lattice spacing (lL), e.g.,lz≫lL, but much smaller than a typical wiggler wavelengthlw, e.g.,lw≫lz. The feasibility of a laser based on this predicted new phenomenon is examined in this letter. Differences between the properties of the proposed quasi‐channeling radiation and radiation produced by wigglers and free‐electron lasers (FEL’s) are discussed. System lengths a factor of 103shorter than FEL’s are expected, with favorable scaling for below 500 eV laser photon output energies. A 500‐eV QCP laser system with a gain of 1 and a length of 1 m is predicted, based on extrapolations of existing storage‐ring technology.