This study focuses on the microstructural features which enhance the resistance of Allvac 718Plus to grain boundary cracking during testing of samples at 704^oC in both dry air and moist air. Fully recrystallized structures were found to be susceptible to brittle grain boundary cracking in both environments. Detailed TEM characterization was performed to reveal features that resist grain boundary cracking in the non-susceptible microstructures. Dislocation substructures found within the grains of non-susceptible structures are suggested to compete with the high angle grain boundaries for oxygen and thereby reducing the concentration of oxygen on grain boundaries and subsequent embrittlement. In addition EBSD misorientation maps also reveal that special boundaries (i.e. Σ3 boundaries) are not embrittled. This is in agreement with previous findings on the superalloy Inconel 718. Furthermore, it is observed that cracks propagate along high angle boundaries. This study also suggests that the presence of delta phase at the grain boundaries does not produce materials that are resistant to grain boundary cracking.