In a small bowl, melt the strawberries and rhubarb (microwave for ~4 minutes). Mash well using a large fork. Add stevia and chia seeds and stir until fully combined. Place in the refrigerator to set.
Line a 4 × 8-inch pan with a large piece of parchment or wax paper (approximately double the size of the pan). Set aside.
In a large bowl, stir together the non-dairy beverage and vanilla until smooth.
Add the oats, wheat bran, psyllium husk, protein, salt, and stevia. Stir to fully combine.
Transfer about 3/4 of the mixture to the pan. Press down very well, using the extra parchment paper to press it evenly into the bottom of the pan.
Pour the prepared fruit mixture (from step 1) evenly on top of the oatmeal layer in the pan.
Sprinkle the remaining oat crumbles on top of the fruit layer. Gently press down using the parchment paper.
Freeze until firm enough to cut 3 x 3 (~1 hour). Enjoy immediately, or return to freezer and store in an airtight container.
For an ideal consistency, if bars are frozen solid from storage, remove from the freezer at least 1 hour before consuming.