We demonstrate terahertz quantum cascade (THz-QC) wire lasers based on dual coupled gratings that achieve continuous-wave (CW) operation near liquid nitrogen temperatures with a low-divergence Gaussian-like beam profile. Our configuration circumvents the effective refractive index constraint, significantly enhancing fabrication efficiency while retaining the key advantages of low power consumption and high heat dissipation efficiency. By engineering the photonic band structure of the coupled gratings, the laser operates on two supermodes. For Supermode #1, grating 1 serves as the master oscillator while grating 2 functions as a phased antenna array, featuring a collimated beam. For Supermode #2, grating 2 is the main oscillator and simultaneously provides a collimated beam, while grating 1 offers high reflectivity. Both supermodes exhibit high cavity quality factors and low beam divergence, achieved with a significantly reduced gain area. Experimentally, both supermodes were observed, and the optimized laser produces a collimated Gaussian beam with divergence angles of 12°×18° and an optical power of 1.04 mW. The threshold power consumption and thermal resistance are as low as 2.62 W and 8.5 mK/W/cm2, respectively, resulting in a maximum CW operating temperature of 78.0 K. This work offers a more accessible route for low-divergence, low-power-consumption, high-thermal-dissipation-efficiency THz-QCLs with enhanced CW operation at elevated temperatures.