Oat Flour (Best Option)
1:1 by volume (1 cup oat flour per 1 cup all-purpose flour)Oat flour contains soluble fibers and some protein which help bind the meat mixture similarly to all-purpose flour. The starches in oat flour absorb moisture and create cohesion in the meatloaf matrix.
To ensure success, use finely ground oat flour and avoid overmixing the meat mixture to prevent a gummy texture. It is best to lightly toast the oat flour beforehand to enhance flavor and reduce any raw oat taste.
Compared to all-purpose flour, oat flour may impart a slightly softer texture and a subtle sweetness, but it generally produces a well-structured, moist meatloaf.