Consider that it takes anywhere from 6 to 20 pounds of feed to get a pound of beef. That's way more resources used, environmental harm done and creatures killed to produce meat.
Only if you replace meat consumption with grains. A quick look at vegan and vegetarian recipes on social media makes it obvious that is not happening. Plants have a 50x range in the amount of calories they provide for $1, which suggests a similar range in their environmental burden.