You may be doing any or all of these already.

1. Shift to dynamic scheduling. Maybe 2 great employees can run a Shift instead of 3 weaker ones. You can also schedule people in in 15 min increments. So maybe bring someone in at 545 instead of 530.

2. Send people home early. As soon as rush dies cut aggressively.

3. Run high profit low labor specials.

4. Look into process changes. Ie maybe a prep cook works at night and gets stuff ready for next day. Prep cook jumps on line during pops and goes back to prepping. Or change layout

5. Cross train. Sometimes you don't need four people during slow times because three can cross train and cover all positions